DE69425474T2 - LC element, semiconductor device, and method for producing the LC element - Google Patents

Description

The present invention relates to an LC element capable of attenuating a predetermined frequency band and used either as part of a semiconductor device or other device or as a discrete element, a semiconductor device including such an LC element, and a method of manufacturing such an LC element.

The rapid advancement of electronic technology in recent years has brought about the use of electronic circuits in an increasingly wide range of fields. Therefore, attempts are being made to ensure stable operation of these electronic circuits without being affected by external conditions.

However, electronic circuits are directly or indirectly subject to the intrusion of external noise. As a result, there exists a problem in which an operation error is caused in electronic products using electronic circuits.

In particular, there are many cases of using switching regulators as DC power supplies for electronic circuits. As a result of transient current generated by such operations as switching or load fluctuations resulting from switching operation of digital ICs used, intense noise having many frequency components is often generated in the power supply line of the switching regulator. This noise is transmitted to other circuits in the same product via the power supply line or by radiation, giving rise to the occurrence of such effects as operation error or deteriorated signal-to-noise ratio and, in some cases, even causing operation errors in other nearby electronic products.

Various types of noise filters are currently used with respect to electronic circuits to remove noise. In particular, as many electronic products of various types have come into use in recent years, the regulations against noise have become more and more stringent, and the development of an LC element having the functions of a compact high-performance noise filter capable of reliably removing such noise is desired.

An example of this type of LC element is an LC noise filter disclosed in Japanese Patent Application Laid-Open No. 3-259608. In the case of this LC noise filter, the L component (inductance) and the C component (capacitance) exist as distributed constants, and compared with a constant-type LC filter concentrated at a point, a preferable attenuation response can be obtained over a relatively wide band.

However, the manufacturing process of this LC noise filter is complicated because this LC noise filter is formed by folding an insulating film which has been provided with the conductor on both sides to form the inductor and the capacitor.

In addition, wiring is required when this LC filter is directly inserted into a power supply line or signal line of an IC or LSI, which requires time and labor to install the components.

In addition, since this LC filter is designed as a discrete component, it is almost impossible to include it in an IC or LSI circuit, i.e., insert it into the internal wiring of an IC, LSI or other device.

Furthermore, in the case of this LC noise filter, since a capacitor formed in the manner of a distributed constant is determined by the corresponding shape and Arrangement of the conductors, which also serve as the inductors, is determined, the capacitance is fixed after the completion of the product. As a result, the problem arises in which the overall characteristics are also fixed and the use for all kinds of applications is limited. For example, to change only the capacitance, the shape of the capacitor type conductor must be changed. Freely changing the capacitance of the LC noise filter connected to a particular circuit according to the requirements is difficult.

EP-A-0 388 985 discloses an LC noise filter comprising a dielectric substrate, a plurality of spiral grooves provided in at least one surface of the substrate, and a plurality of inductance conductors provided in the corresponding spiral grooves. The inductance conductors are opposed to each other with the side wall of the grooves interposed therebetween.

US-A-3 022 472 is directed to a variable equalizer using a semiconductive element. According to one embodiment, a p-type dopant is diffused into the surface of an n-type wafer. A base electrode of conductive metal is disposed on the lower surface of the wafer. The diffusion region partially comprises a spiral section covered by a metallic deposit connected to a terminal.

The present invention takes the above-mentioned points into consideration and its objects are to provide an LC element and a semiconductor device which enable simplified manufacturing, eliminate operations for assembling the parts in subsequent processing, and can be formed as a part of an IC or LSI device, and to provide a manufacturing method for such an LC element.

Another object of the present invention is to provide an LC element, a semiconductor device and an LC element manufacturing method which enable that the characteristics can be changed by changing the distributed capacitance and/or constant type resistance according to the requirements.

To solve the above-mentioned problems, the invention provides an LC element as defined in claim 1, 2, 12 or 13.

In the case of the LC element of claim 1, the first and second electrodes having predetermined shapes are formed substantially in parallel on the semiconductor substrate surface. In addition, an insulating layer is formed between at least one of these two electrodes and the semiconductor substrate. The first or second electrode, the insulating layer and the semiconductor substrate form a MOS structure.

Generally, a conductor acts as an inductor by forming it into a spiral shape. However, by modifying the conductor shape or when a particular frequency band is used, the function of an inductor can be obtained with conductor shapes other than spiral.

In this way, with respect to the LC element according to this invention, the second electrode and the channel formed corresponding to the first electrode, which have a predetermined shape, can function as inductors, respectively. In addition, in the same manner as an ordinary MOSFET, since a depletion layer is formed in the outer periphery of the channel, a distributed constant type capacitor is formed between the channel and the surrounding semiconductor substrate. In addition, the semiconductor substrate is directly or indirectly connected to the second electrode via an insulating layer, thereby forming a distributed constant type capacitor between the channel and the second electrode.

As a result, when a signal input to the first or second diffusion region formed at one end of the channel is transmitted through the inductances and distributed constant type capacitors, excellent attenuation characteristics over a wide band can be obtained.

In particular, this LC element can be manufactured by forming the first or second diffusion region on a semiconductor substrate, and then forming the insulating layer and the first and second electrodes having predetermined shapes on this surface. The manufacturing is thus extremely easy. In addition, since this LC element is formed on a semiconductor substrate, it can be formed as a portion of an IC or LSI device, and when formed in this manner, the work for assembling the parts in subsequent processing can be shortened.

Unlike the above-mentioned LC element in which the channel is used as the signal transmission line, in the LC element according to claim 12, the second electrode is used as the signal transmission line, and since the signal is not transmitted through the channel, either the first or second diffusion region is omitted.

As a result, in the same manner as the above-mentioned LC element, the channel and the second electrode act as inductors, respectively, and a distributed constant type capacitor is formed between them. This LC element thus has excellent attenuation characteristics over a wide band, while the fabrication is easy and it can be formed as a portion of a substrate.

Compared with the above-mentioned LC element in which the first and second electrodes having predetermined shapes are arranged substantially in parallel on the same plane, in the case of the LC element according to claim 2, they are arranged substantially oppositely across the semiconductor substrate. The channel formed corresponding to the first electrode and the second electrode respectively function as inductors while a depletion layer is formed between them. to form a distributed constant type capacitor. As a result, this LC element has excellent attenuation characteristics over a wide band, the fabrication is easy, and it can be formed as a section of a substrate. In addition, the required semiconductor substrate surface area can be made smaller compared to the above-mentioned LC element.

In the case of the LC element according to claim 13, too, the first and second electrodes having predetermined shapes are arranged substantially oppositely across the semiconductor substrate. The channel formed corresponding to the first electrode and the second electrode function as inductors respectively, while a distributed constant type capacitor is formed between them. As a result, this LC element has excellent attenuation characteristics over a wide band, the manufacture is easy, and it can be formed as a portion of a substrate. In addition, the required semiconductor substrate surface area can be made small.

According to another aspect of this invention, in the case of the above-mentioned LC elements in which the first and second electrodes are formed on the same side of the semiconductor substrate, an inversion layer having an n-type region or a p-type region is formed along the first and second electrodes.

This LC element is different in type from the above-mentioned LC element in which the first and second electrodes are formed on the same side of the semiconductor substrate and a single layer having an n-region or a p-region is used, in that a semiconductor substrate having an inversion layer having an n-region or a p-region of a predetermined shape formed along the first and second electrodes is used. In other words, when adjacent inversion layers having a predetermined shape are noticed, since an npn or pnp construction is formed, excellent isolation can be obtained. As a result, the state in which a con distributed constant type capacitor formed only between the second electrode disposed adjacent to the channel formed corresponding to the first electrode can be easily manufactured, and this LC element can have excellent attenuation characteristics over a wide band.

According to another aspect of this invention, in the case of the above-mentioned LC elements in which the first and second electrodes are respectively formed on opposite sides of the semiconductor substrate, the semiconductor substrate has an inversion layer having either an n-type region or a p-type region formed between the adjacent conductor portions of the first electrode and between the adjacent conductor portions of the second electrode.

Compared with the above-mentioned type of LC element in which the first and second electrodes are respectively formed on opposite sides of the semiconductor substrate, this LC element is different in that an inversion layer is formed between adjacent first and second electrodes in the semiconductor substrate. In other words, except for the substantially opposed channel and the second electrode, since there is a connection via an interposed npn or pnp construction, excellent isolation can be obtained. As a result, a state in which a distributed constant type capacitor is formed only between the pair of the opposed channel and the second electrode can be easily produced. This LC element can be formed to have excellent attenuation characteristics over a wide band.

The shapes of the first and second electrodes of the above-mentioned LC elements according to this invention include spiral, meander, curved line and straight line shapes.

By using spiral shapes for the first and second electrodes, adjacent electrodes can be positioned close to each other, thus efficiently utilizing the space. ciently used. Even when meandering or wave-like shapes are used for the first and second electrodes, each convex or concave bend has approximately 1/2 turn of a coil, and since they are connected in series, a predetermined inductance can be obtained as a whole. Furthermore, in cases where use is limited to a high frequency band, even curved line-like or straight line-like electrodes can have predetermined inductances and operate in the same manner as spiral electrodes.

In the case of the LC element according to claim 9, the first and second input/output electrodes are respectively connected to the first and second diffusion regions near the respective ends of the channel formed corresponding to the first electrode, and by providing the ground electrode near the one end of the second electrode, a three-terminal type LC element using the channel as the signal transmission line can be easily provided.

In the case of the LC element according to claim 20, the first and second input/output electrodes are respectively provided near the respective ends of the second electrode, and by providing the ground electrode connected to the first or second diffusion region formed near one end of the channel, a three-terminal type LC element using the second electrode as the signal transmission line can be easily provided.

In the case of the LC element according to claim 10, together with the provision of the first and second input/output electrodes respectively for the first and second diffusion regions formed at the respective ends of the channel, by providing third and fourth input/output electrodes respectively near the respective ends of the second electrode, a four-terminal common mode type LC element can be easily provided.

In the case of the LC element according to claim 11, the second electrode is divided into a plurality of electrode segments and portions thereof are electrically connected. In this case, the self-inductance area of each divided segment is small and a distributed constant type LC element can be provided in which the influence of this self-inductance is small.

In the case of the LC element according to claim 21, by dividing the first electrode into a plurality of electrode segments, the channel formed corresponding thereto can also be divided into a plurality of segments. As a result, the self-inductance area of each divided channel segment is small, and a distributed constant type LC element can be easily provided in which the influence of this self-inductance is small.

In the case of the LC element according to claim 22, by variably setting the gate voltage applied to the first electrode, the width, i.e., the resistance, of the channel having a predetermined shape and formed corresponding to the first electrode is varied. In addition, since variation occurs in the depletion layer formed in the vicinity of the channel, the capacitance of the capacitor formed between the channel and the second electrode can also be varied. As a result, by varying the gate voltage, the channel resistance and the capacitance of the distributed constant type capacitor formed between the channel and the second electrode can be varied, thereby allowing variable control of the attenuation characteristics according to requirements.

In the case of the LC element according to claim 23, a depletion type element is formed by injecting carriers into a position corresponding to the first electrode. Without changing the characteristics of the LC element itself, the channel may be formed in the state where no voltage (gate voltage) is applied to the first electrode, or the relationship between the applied gate voltage and the channel width and the like may be changed.

In the case of claim 24, either the first or the second electrode is formed shorter than the other electrode, and in this case also the first and the second electrodes having respective different lengths function as inductors, and a distributed constant type capacitor is formed between these electrodes via a depletion layer. As a result, this LC element has excellent attenuation characteristics over a wide band, while the manufacture is easy and the LC element can be formed as a portion of a substrate.

In the case of claim 25, a buffer for amplifying the signal output through the channel of an above-mentioned LC element is connected. The voltage level of a signal attenuated by the relatively high resistance of the channel (compared to a metallic material such as aluminum) can be restored with an excellent SN (signal-to-noise) ratio.

In the case of claim 26, a protection circuit is connected to at least the first or second electrode, and when an excessive voltage is applied to these electrodes, a bypass current flows on the side of the operating power supply side or the ground side. As a result, insulation breakdown between the first or second electrode and the semiconductor substrate can be prevented.

According to claim 27, terminals are formed by forming an insulating layer on the entire surface, openings in portions of the insulating layer are opened by etching or by emitting laser light, and the openings are closed by applying solder to the extent that it protrudes slightly from the surface.

In the manufacturing process, after the LC element is formed on the semiconductor substrate, the insulating layer is deposited on the entire surface by a process such as a chemical liquid phase deposition. The openings are opened in portions of the insulating layer by etching or by emitting laser light, and then solder is deposited into the openings to provide terminals. As a result, the surface mount type LC element can be easily manufactured, in which case the work of installing the LC element is also easy.

In the case of the semiconductor device according to claim 28, any of the above-mentioned LC elements is formed as a portion of a substrate so as to be inserted into a signal line or a power supply line. As a result, the LC element can be formed in a unified manner with other components on the semiconductor substrate. The manufacture is easy while parts of the work for assembling in subsequent processing are unnecessary.

An LC element manufacturing method according to this invention comprises the steps as defined in claim 29 or 30.

The two LC element manufacturing methods mentioned above are suitable for manufacturing the above-mentioned LC elements by applying the semiconductor manufacturing technology. In other words, in the first process, either one or both of the first and second diffusion regions are formed on the semiconductor substrate; in the second process, the insulating layer and the first and second electrodes are formed on the semiconductor substrate surface; and in the third process, the LC element is completed by forming the wiring layer containing input/output electrodes and the like.

In this way, the above-mentioned LC elements can be manufactured by using ordinary semiconductor manufacturing technology (especially MOS manufacturing technology). In addition to enabling a reduction in size and a reduction in cost, a plurality of individual LC elements can be mass-produced simultaneously.

Fig. 1 is a plan view of an LC element according to a first embodiment of this invention;

Figs. 2A and 2B are enlarged sectional views taken along line A-A in Fig. 1;

Fig. 3 is an enlarged sectional view taken along line B-B in Fig. 1;

Fig. 4 is an enlarged sectional view taken along the line C-C in Fig. 1;

Fig. 5 is an enlarged sectional view taken along line D-D in Fig. 1 ;

Fig. 6 shows a cross-sectional structure in the longitudinal direction of an LC element according to the first embodiment of this invention;

Figs. 7A, 7B and 7C are schematic diagrams showing equivalent circuits of the LC elements according to the first embodiment;

Figs. 8A and 8B are descriptive drawings for describing the channel resistance;

9A to 9G show an example of a manufacturing process for an LC element according to the first embodiment;

Fig. 10 shows an example of a variation of an LC element according to the first embodiment;

Fig. 11 shows an example of a variation of an LC element according to the first embodiment;

Fig. 12 is an enlarged sectional view taken along line A-A in Fig. 11 ;

Fig. 13 shows an example of a variation of an LC element according to the first embodiment;

Fig. 14 is a plan view of an LC element according to a second embodiment of this invention;

Fig. 15 is an enlarged sectional view taken along line B-B in Fig. 14 ;

Fig. 16 is an enlarged sectional view taken along the line C-C in Fig. 14 ;

Fig. 17 shows the principle of an inductance formed by a meander-shaped electrode;

Fig. 18 shows an example of a variation of an LC element according to the second embodiment;

Fig. 19 shows an example of a variation of an LC element according to the second embodiment;

Fig. 20 shows an example of a variation of an LC element according to the second embodiment;

Fig. 21 is a plan view of an LC element according to a third embodiment of this invention;

Fig. 22 is a schematic diagram showing an equivalent circuit of the LC element according to the third embodiment;

Fig. 23 shows an example of a variation of an LC element according to the third embodiment;

Fig. 24 shows an example of a variation of an LC element according to the third embodiment;

Fig. 25 shows an example of a variation of an LC element according to the third embodiment;

Fig. 26 is a plan view of an LC element according to a fourth embodiment of this invention;

Fig. 27 shows an example of a variation of an LC element according to the fourth embodiment;

Fig. 28 shows an example of a variation of an LC element according to the fourth embodiment;

Fig. 29 shows an example of a variation of an LC element according to the fourth embodiment;

Fig. 30 is a plan view of an LC element according to a fifth embodiment of this invention;

Fig. 31 is a schematic diagram showing an equivalent circuit of the LC element according to the fifth embodiment;

Fig. 32 shows an example of a variation of an LC element according to the fifth embodiment;

Fig. 33 is a plan view of an LC element according to a sixth embodiment of this invention;

Fig. 34 shows an example of a variation of an LC element according to the sixth embodiment;

Fig. 35 is a plan view of an LC element according to a seventh embodiment of this invention;

Fig. 36 is a schematic diagram showing an equivalent circuit of the LC element according to the seventh embodiment;

Fig. 37 shows an example of a variation of an LC element according to the seventh embodiment;

Fig. 38 is a plan view of an LC element according to an eighth embodiment of this invention;

Fig. 39 shows an example of a variation of an LC element according to the eighth embodiment;

Figs. 40A, 40B, 41A and 41B are plan views of LC elements according to a ninth embodiment of this invention;

Fig. 42 shows an example of a variation of an LC element according to the ninth embodiment;

Fig. 43 shows an example of a variation of an LC element according to the ninth embodiment;

Fig. 44 shows an example of a variation of an LC element according to the ninth embodiment;

Figs. 45 and 46 show examples of variations in which the input/output electrode positions are changed;

Figs. 47 and 48 are abbreviated views of the provision of terminals by a chemical liquid phase deposition;

Fig. 49 is an explanatory drawing of forming LC elements of each embodiment as sections of an LSI or other device;

50A to 50D are schematic diagrams showing examples of a buffer circuit connection to the output side of the LC elements of each embodiment;

51A and 51B are schematic diagrams showing examples of protection circuit connection to the input side of the LC elements of each embodiment;

Figs. 52A and 52B are sectional views showing a construction when an inversion layer is formed in the semiconductor substrate;

Fig. 53 is a sectional view showing a construction when an inversion layer is formed in the semiconductor substrate; and

Fig. 54 shows partial sectional views when etching is performed on a portion of the substrate.

DETAILED DESCRIPTION OF THE INVENTION

The following is a description of the preferred embodiments of the LC elements according to this invention with reference to the accompanying drawings. Since the construction of the LC elements according to this invention corresponds to a MOSFET, the terminology relating to a field effect transistor is used in the following description, in other words, one diffusion region is referred to as the source, the other diffusion region is referred to as the drain, and the gate electrode is referred to as the gate, respectively. Hence, in the following description, the source and the drain are substantially equivalent and these may be interchanged.

FIRST EMBODIMENT

Fig. 1 is a plan view of an LC element according to a first embodiment of this invention. Figs. 2, 3, 4 and 5 are enlarged sectional views taken along lines AA, BB, CC and DD in Fig. 1, respectively. As shown in Figs. As shown, the LC element 100 of this embodiment includes a source 12 and a drain 14 formed in separate positions near the surface of a semiconductor substrate 30 comprising p-type silicon (p-Si) and which are connected by a channel 22 formed by applying a voltage to a spiral-shaped first electrode 10 disposed therebetween.

The source 12 and the drain 14 are formed as inverted n+ regions of the p-Si substrate 30. For example, these are formed by increasing the dopant concentration by injecting As+ ions by thermal diffusion or ion implantation. The first electrode 10 functions as a gate and is formed on an insulating layer 28 formed on the surface of the p-Si substrate 30 in a manner in which one end of the spiral shape overlaps the source 12 and the other end overlaps the drain 14. The first electrode 10 is formed by aluminum or another layer, or by heavily p-doping by diffusion or ion injection.

In addition, the insulating layer 28 on the surface of the p-Si substrate 30 serves to insulate the p-Si substrate 30 and the first electrode 10. As indicated in Fig. 2A, except for the second electrode 26 (described below), the insulating layer 28 covers the entire surface of the p-Si substrate 30. In addition, the first electrode 10 is formed on the surface of this insulating layer 28. The insulating layer 28 comprises, for example, SiO₂ to which p is added (P-glass).

The second electrode 26 is formed substantially parallel to the first electrode 10. By applying a predetermined gate voltage between the second electrode 26 and the first electrode 10, the channel 22 is formed on the surface of the p-Si substrate 30 so as to face the first electrode 10.

As shown in Figs. 1 to 6, a ground electrode 16, input/output electrodes 18 and 20 and a control electrode 24 are respectively connected to the first E electrode 10, the source 12, the drain 14 and the second electrode 26. In order not to damage the thin gate layer, the attachment of the control electrode 24 to the first electrode 10 is carried out outside the active region, as shown in Fig. 1. Furthermore, as shown in Figs. 3 and 5, after exposing a part of the source 12 and the drain 14, the attachment of the input/output electrode 18 to the source 12 and the attachment of the input/output electrode 20 to the drain 14 are carried out by depositing aluminum or another metal layer. In addition, in the same manner as the control electrode 24, the attachment of the ground electrode 16 to the second electrode 26 is carried out in a position separated from the active region, in order not to damage the thin gate layer.

By using an n-channel enhancement structure for an LC element 100 having the above-mentioned structure, the channel 22 is formed when a positive voltage is applied to the first electrode 10.

2A and 2B show the state of forming the channel 22. As shown in Fig. 2A, in the state where a positive gate voltage is not applied to the first electrode 10, that is, to the control electrode 24 connected to the first electrode 10, the channel 22 does not appear in the surface of the p-Si substrate 30. As a result, in this state, the source 12 and the drain 14 shown in Fig. 1 are isolated (separated).

Conversely, when a positive gate voltage is applied to the first electrode 10 as shown in Fig. 2B, the channel 22 having an n-region appears near the surface of the p-Si substrate 30 corresponding to the first electrode 10. In addition, by applying this positive gate voltage to the first electrode 10, positive holes are removed so that a depletion layer 32 is formed on the outside of the channel 22 in the p-Si substrate 30. As a result, the electrons in the channel 22 and the positive holes in the p-Si substrate 30 are opposed to each other on opposite sides of this depletion layer 32 to form a capacitor. In addition, since this capacitor is formed over substantially the entire length of the first electrode 10, a distributed constant type capacitor is formed between the second electrode 26 connected to the p-Si substrate 30 and the channel 22.

The gate voltage applied to the first electrode 10 is positive with respect to the voltage of the p-Si substrate 30, i.e., the voltage applied to the second electrode 26 formed in the surface of the p-Si substrate 30. In addition, in order to have a connection between the source 12 and the drain 14 through the channel 22, a relatively positive voltage is also required with respect to the source 12 and the drain 14.

Fig. 6 shows the cross-sectional construction of the LC element 100 as viewed in the longitudinal direction of the first electrode 10. As shown in the figure, the channel 22 is formed parallel to the electrode 10 and the conductive state is created between the source 12 and the drain 14 through this channel 22. For example, in the case of an enhancement type, the channel 22 is formed in the state with the gate voltage applied to the first electrode 10 and the conductive state is created between the source 12 and the drain 14. By varying the gate voltage applied to the first electrode 10, since the width and the depth of the channel 22 are changed, the resistance between the source 12 and the drain 14 can be varied.

In addition, as indicated in Fig. 2B, by changing the width and depth of the channel 22, the surface area of the channel 22 is also changed and as a result, the surface area of the depletion layer 32 is changed. In other words, due to this change in the surface area, the capacitance of the distributed constant type capacitor formed between the channel 22 and the second electrode 26 changes and as a result, the capacitance can also be varied by changing the gate voltage.

In an LC element 100 having this type of construction, the channel 22 formed corresponding to the spiral first electrode 10 and the second electrode 26 function as inductors, respectively. In addition, a capacitor is formed between the channel 22 and the second electrode 26 on opposite sides of the depletion layer 32 formed on the outer periphery of the channel 22. As a result, the inductors formed by the channel 22 and the second electrode 26 and the capacitor formed opposite to the depletion layer 32 exist as distributed constants.

7A, 7B and 7C show equivalent circuits for the LC element 100 of the first embodiment. In the equivalent circuit of Fig. 7A, the channel 22 is formed by applying a predetermined gate voltage to the control electrode 24. The channel 22 is used as the signal transmission line while the ground electrode 12 is grounded, thereby providing the functions as a three-terminal type element.

In this case, the channel 22 functions as an inductor having the inductance L1, while the second electrode 26 functions as an inductor having the inductance L2. Between these two inductors, a distributed constant type capacitor having a predetermined capacitance C is formed. As a result, this LC element 100 is capable of superb attenuation characteristics not found in conventional concentrated constant type elements. Only the predetermined frequency components are removed from an input signal applied to one of the input/output electrodes 18 and 20 and obtained as an output from the other of these electrodes.

Although Fig. 7A shows the ground electrode 16 as being connected to ground, the ground electrode 16 may also be connected to a power supply having a predetermined potential.

Fig. 7B shows an equivalent circuit when a control voltage Vc is applied to the control electrode 24. The control voltage Vc applied to the control electrode 24 is the gate voltage itself, and since the depth of the channel 22 is varied by varying this voltage Vc, the mobility of the channel 22 is changed and as a result, the resistance between the source 12 and the drain 14 can be varied as desired. At the same time, the capacitance C between the channel 22 and the second electrode 26 can also be changed in the same manner as described above.

As a result, the overall attenuation characteristics of the LC element 100 can be changed by changing the resistance of the channel 22 and the distributed constant type capacitance C between the channel 22 and the second electrode 26. In other words, by changing this control voltage Vc, the characteristics of the LC element 100 can be changed as desired within a certain range.

Fig. 7C shows another circuit functionally equivalent to that in Fig. 7B. By changing the control voltage Vc, the resistance of a variable resistor connected in series with the channel 22 and the capacitance of the variable distributed constant type capacitor formed between the channel 22 and the second electrode 26 can be varied.

The above description refers to an LC element 100 in which an n-channel is formed between the source 12 and the drain 14, in which case the mobility of the electrons used as carriers is high and the resistance of the channel 22 is small. Conversely, the above-mentioned LC element 100 may also have a p-channel formed on an n-Si substrate. In this case, since holes are used as the carriers, the resistance of the channel 22 is comparatively large, and the characteristics are different from the above-mentioned case of the n-channel.

Figs. 8A and 8B are descriptive drawings for describing the resistance R of the channel 22 when the depth of the channel 22, etc. are changed by varying the gate voltage (control voltage) applied to the first electrode 10. Fig. 8A is a plan view in which the actual spiral-shaped first electrode 10 is changed into a straight shape for the purpose of description. Fig. 8B is a cross-sectional view taken along the line A-A in Fig. 8A.

In Figs. 8A and 8B, W is the gate width and X is the channel depth. In this way, if the channel 22 is formed by the first electrode 10 having the width W, the width of this channel becomes equal to (W + 2X). As a result, the resistance R of the channel 22 between the source 12 and the drain 14 can be calculated as follows.

R = ρ/(W + 2X)

In the above, p is the resistance per unit area of the channel 22, and it is shown that the channel resistance R is proportional to the channel length L and inversely proportional to the channel width (W + 2X).

The following is a description of a manufacturing process for the LC element 100 according to this embodiment.

9A to 9G show an example of a manufacturing process for an enhancement-type LC element 100. The figures show cross sections of the spiral-shaped gate electrode 10 viewed in the longitudinal direction.

(1) Formation of an oxidized layer:

First, silicon dioxide SiO2 is formed on the surface of the p-Si substrate 30 by thermal oxidation (Fig. 9A).

(2) Opening the source and drain windows:

Portions corresponding to the source 12 and the drain 14 are opened by photoetching the oxidized layer on the surface of the p-Si substrate 30 (Fig. 9B).

(3) Source and drain formation:

The source 12 and drain 14 are formed by injecting n-type dopant into the opened portions (Fig. 9C). For example, As+ is used as the n-type dopant and is injected by thermal diffusion. If the dopants are injected by ion implantation, the window opening of Fig. 9B is not required.

(4) Removing the gate area:

A gate opening portion is formed by removing the oxidized film from the region for forming the spiral gate electrode 10 (Fig. 9D). In the case of this embodiment, the gate opening portion is also formed in a spiral shape corresponding to the spiral gate electrode 10. In this way, only the portion of the p-Si substrate 30 corresponding to the spiral gate electrode 10 is exposed.

(5) Gate oxidation layer formation:

A new oxidation layer, i.e., the insulation layer 26, is formed on the partially exposed p-Si substrate 30 (Fig. 9E).

(6) Gate and electrode formation:

The spiral gate electrode 10 acting as a gate is formed, for example, by vapor deposition of aluminum or other material, as are the input/output electrode 18 connected to the source 12 and the input/output electrode 20 connected to the drain 14 (Fig. 9F).

Before, after, or in parallel with steps 4 to 6, a window is opened in the portion corresponding to the second electrode 26, and the second electrode 26 and the ground electrode 16 connected thereto are formed.

(7) Insulation layer formation:

Finally, P-glass is deposited over the entire surface, after which heating provides a smooth surface (Fig. 9G).

In this way, the manufacturing process of the LC element 100 is basically the same as the ordinary MOSFET manufacturing process, and it can be said to be different only in the shape and other qualities of the first electrode 10. As a result, formation on the same substrate with an ordinary MOSFET or ordinary bipolar transistor is enabled, and formation as a portion of an IC or LSI device is possible. Moreover, when it is formed as a portion of an IC or LSI device, the assembling processes in subsequent processing can be omitted.

As explained, in the LC element 100 according to this embodiment, the channel 22 formed corresponding to the first electrode 10 and the second electrode 26 have inductances, respectively, while a distributed constant type capacitor is formed between the channel 22 and the second electrode 26.

As a result, in a case where the ground electrode 16 provided at one end of the second electrode 26 is grounded or connected to a fixed potential and the channel is used as the signal transmission line, the resulting LC element has excellent attenuation characteristics with respect to the input signal over a wide band.

As also mentioned above, since this LC element can be manufactured by using an ordinary MOSFET manufacturing technology, the manufacturing is both easy and applicable to downsizing and other requirements. In addition, when the LC element is manufactured as a section of a semiconductor substrate, the wiring with other components can be carried out simultaneously, and the assembly and other work during subsequent processing becomes unnecessary.

Also with respect to the LC element 100 of this embodiment, the resistance value of the channel 22 and the capacitance of the distributed constant type capacitor formed between the channel 22 and the second electrode 26 can be variably controlled by changing the gate voltage (control voltage Vc) applied to the first electrode 10, and the overall frequency response of the LC element 100 can be adjusted or changed.

In the foregoing description of the first embodiment, the channel 22 formed corresponding to the first electrode 10 was used as the signal transmission line, but it is also acceptable to exchange the functions of the channel 22 and the second electrode 26. In other words, as shown in Fig. 10, by respectively connecting the input/output electrodes 18 and 20 to the corresponding ends of the second electrode 26, by connecting the ground electrode 16 to the source 12 (or drain 14) formed at one end of the channel 22, then by connecting the ground electrode 16 to ground or a fixed Potential, the second electrode 26 can be used as the signal transmission line. However, in this case, since either the source 12 or the drain 14 is connected to the ground electrode 16, the other element may be omitted.

Fig. 11 shows an example of a variation of the first embodiment in which the second electrode 26 is arranged to be substantially opposite to the first electrode 10 on the opposite (rear) side of the p-Si substrate 30. For the purpose of illustration, in order to recognize the shape of the rear electrode, the position is slightly shifted to the lower right in the figure. Fig. 12 is an enlarged sectional view taken along the line A-A in Fig. 1, and corresponds to Fig. 2. Fig. 13 shows an example using the LC element shown in Fig. 11 in which the second electrode 26 is used as the signal transmission line, and corresponds to Fig. 10.

In this way, even if the spiral-shaped first and second electrodes are arranged substantially opposite each other on opposite sides of the p-Si substrate 30, i.e., the channel 22 and the second electrode 26 are arranged substantially opposite each other, in the same manner as the LC element 100 shown in Fig. 1 and others, the channel 22 and the second electrode 26 function as inductors respectively while a distributed constant type capacitor is formed between them. As a result, an LC element having such advantages as excellent frequency response and ease of manufacture can be obtained. Particularly, when the first and second electrodes are arranged substantially opposite each other in this way, the advantage of a reduced installation area is obtained as compared with the case where they are arranged substantially in parallel on the same plane as shown in Fig. 1.

SECOND EMBODIMENT

A description will now be given of an LC element according to a second embodiment of this invention with reference to the accompanying drawings.

An LC element according to the second embodiment differs from the first embodiment mainly by using non-spiral shapes for the first electrode 10 and the second electrode 26. Of course, the channel formed along the first electrode 10 is also of a non-spiral shape. In the figures, the same designations are used for items corresponding to those of the first embodiment.

Fig. 14 is a plan view of an LC element according to the second embodiment. Figs. 15 and 16 are enlarged sectional views taken along the lines B-B and C-C in Fig. 14, respectively. The enlarged sectional view taken along the line A-A in Fig. 14 is the same as that of the first embodiment shown in Figs. 2A and 2B.

Fig. 17 shows the principle of an inductor formed by a meandering electrode. When current flows in a single direction in a meandering electrode 10 having concave and convex bends, a magnetic flux is alternately generated such that the direction is reversed in adjacent concave and convex bends (for example, vertically upward from the figure near the locations shown by circled dots in Fig. 17 and vertically downward near the locations shown by circled X), whereby the situation resembles the state when 1/2 coil turns are connected in series. As a result, an element having a meandering shape as shown in Fig. 17 can be made to function as an inductor having a predetermined total inductance.

Also, in the case of a spiral electrode, one of the electrode ends is positioned near the central portion, and the other end is positioned at the peripheral portion. In contrast, in the case of a meander-shaped electrode, since both of the electrode ends are positioned at the peripheral portion, the arrangement for providing the terminals and for connecting to other circuit components is preferable.

In this way, in the case of the LC element 200 of this embodiment, in the same manner as the LC element 100 of the first embodiment, the channel 22 formed corresponding to the first electrode 10 and the second electrode 26 act as inductors, respectively, while a distributed constant type capacitor is formed between the channel 22 and the second electrode 26.

As a result, in the case where the channel 22 is used as the signal transmission line, while the ground electrode 16 provided at one end of the second electrode 26 is grounded or connected to a fixed potential, an LC element having excellent attenuation over a wide band with respect to the input signal is obtained.

In addition, as shown in Fig. 18, without using the channel 22 formed corresponding to the first electrode 10 as the signal transmission line, by connecting the input/output electrodes 18 and 20 to the corresponding ends of the second electrode 26, connecting the ground electrode 16 to the source 12 (or drain 14) formed at one end of the channel 22, and connecting the ground electrode 16 to ground or a fixed potential, the second electrode 26 can also be used as the signal transmission line in the same manner as the LC 100 of the first embodiment.

Fig. 19 shows an example of a variation of the second embodiment in which the second electrode 26 is arranged such that it faces the first electrode 10 on the opposite set (rear) side of the p-Si substrate 30. For the purpose of illustration, to enable recognition of the shape of the rear electrode, the position is slightly shifted to the lower right in the figure. An enlarged sectional view taken along the line AA in Fig. 19 is the same as in Figs. 12A and 12B. Fig. 20 shows an example in which the second electrode 26 of the LC element of Fig. 19 is used as the signal transmission line, and it corresponds to Fig. 18.

In this way, even if the meander-shaped first and second electrodes are arranged substantially opposite to each other on opposite sides of the p-Si substrate 30, that is, the channel 22 and the second electrode 26 are arranged substantially opposite to each other, in the same manner as the LC element 200 shown in Fig. 14 and others, the channel 22 and the second electrode 26 respectively function as inductors while a distributed constant type capacitor is formed between them. As a result, an LC element having such advantages as excellent frequency response and easy manufacturing can be obtained. In particular, when the first and second electrodes 10 and 26 are arranged substantially opposite to each other in this way, the advantage of a reduced installation area can be obtained compared with the case where they are arranged substantially in parallel on the same plane as shown in Fig. 14.

In addition, as mentioned above, since this LC element 200 can be manufactured by using ordinary MOSFET manufacturing technology, production is both easy and applicable to size reduction and other requirements. In addition, when the LC element is manufactured as a section of a semiconductor substrate, wiring with other components can be carried out simultaneously, and assembly and other work during subsequent processing become unnecessary. By varying the gate voltage (control voltage Vc) applied to the first electrode 10, the resistance of the channel 22 and the channel 24 can be varied. capacitance of the distributed constant type capacitor formed between the channel 22 and the second electrode 26 can be variably controlled, thereby enabling the overall frequency response of the LC element 200 to be adjusted or changed as in the LC element 100 of the first embodiment.

THIRD EMBODIMENT

The following is a description of an LC element according to a third embodiment of this invention with reference to the accompanying drawings.

In the above-described first and second embodiments, referred to as LC elements 100 and 200, respectively, the channel 22 formed corresponding to the first electrode 10 and the second electrode 26 were substantially parallel over their entire length, and therefore were formed to have substantially the same length. In the case of an LC element 300 of the third embodiment, the second electrode 26 is formed to have approximately 1/2 the length shown in Fig. 1.

Fig. 21 is a plan view of an LC element 300 according to the third embodiment. As shown in the figure, even if a portion of the second electrode 26 is omitted, the shortened second electrode 26 and the channel 22 formed longer than the second electrode 26 corresponding to the first electrode 10 have inductances, respectively, while a distributed constant type capacitor is formed by the channel 22 and the second electrode 26. Therefore, excellent attenuation characteristics are obtained as in the LC element 100 of the first embodiment shown in Fig. 1.

Fig. 22 shows an equivalent circuit of the LC element 300. As shown in the figure, the inductance L3 is reduced only to the extent that the number of turns of the second electrode 26 is reduced, while the corresponding distributed constant type capacitance C1 is also reduced.

In addition, by varying the gate voltage applied to the control electrode 24, the resistance of the channel 22 formed corresponding to the first electrode 10 and the capacitance between the channel 22 and the second electrode 26 having the reduced turns are varied, thereby enabling the attenuation characteristics of the LC element 300 to be variably controlled as in the LC elements 100 and 200 of the respective first and second embodiments described above.

In this way, the channel 22 formed corresponding to the first electrode 10 and the second electrode 26 formed shorter than the first electrode 10 have inductances while a distributed constant type capacitor is formed between them, thereby enabling the LC element 300 to function as an element having excellent attenuation characteristics.

The above description refers to an LC element 300 in which the channel 22 formed corresponding to the first electrode 10 is used as the signal transmission line. However, it may also be arranged so that the second electrode 26 is used as the signal transmission line and the channel 22 formed corresponding to the first electrode 10 is connected to ground or a fixed potential.

Fig. 23 shows an example of a variation in which the second electrode 26 is used as the signal transmission line, and it corresponds to Fig. 10 of the first embodiment. In this case, the respective input/output electrodes 18 and 20 are connected to the respective ends of the second electrode 26, while the ground electrode 16 is connected to the source 12 (or the drain 14) provided at one end of the channel 22 formed corresponding to the first electrode 10.

By forming the first electrode 10 with approximately half the length of the second electrode 26, the channel 22 formed corresponding to the first electrode 10 is also formed with approximately half the length.

Even in this case, the channel 22 formed corresponding to the first electrode 10 and the second electrode 26 will also act as inductors respectively while a distributed constant type capacitor is formed between them. Therefore, excellent attenuation characteristics can be obtained in the same manner as in the LC element 300 shown in Fig. 21.

Fig. 24 shows an example of a variation in which the shortened second electrode 26 is arranged substantially opposite to the first electrode 10 (i.e., the channel 22) on the opposite surface of the p-Si substrate 30, and corresponds to Fig. 21. Fig. 25 corresponds to Fig. 23 and shows an example of a variation in which the second electrode 26 is arranged substantially opposite to the first electrode 10 on the opposite surface of the p-Si substrate 30, and the first electrode 10 and the channel 22 formed corresponding thereto are shortened.

As shown in Figs. 24 and 25, even if the spiral channel 22 and the spiral second electrode 26 of different lengths are arranged substantially oppositely, the channel 22 and the second electrode 26 respectively function as an inductor in the same manner as in the LC element 300 shown in Fig. 21 and others while a distributed constant type capacitor is formed between them, thereby providing such advantages as excellent frequency response and ease of manufacture.

The LC element 300 also offers the same advantages as the LC elements 100 and 200 of the respective first and second embodiments, such as the ability to be manufactured by using semiconductor manufacturing technology and the ability to form as a section of an LSI or other device, in which case the wiring work in subsequent processing can be shortened.

FOURTH EMBODIMENT

The following is a description of an LC element according to a fourth embodiment of this invention with reference to the accompanying drawings.

An LC element according to the fourth embodiment differs from the third embodiment mainly by using non-spiral shapes for the first electrode 10 and the second electrode 26. The channel 22 formed along the first electrode 10 is also shaped in a non-spiral shape. In the figures, the same designations are used for items corresponding to those of the third embodiment.

In the case of an LC element 400 of the fourth embodiment, the second electrode 26 is formed to be about 1/2 the length in the second embodiment shown in Fig. 14.

Fig. 26 is a plan view of an LC element 400 according to the third embodiment. As shown in the figure, even if a portion of the second electrode 26 is omitted, the shortened second electrode 26 and the channel 22 formed longer than the second electrode 26 corresponding to the first electrode 10 have inductances, respectively, while a distributed constant type capacitor is formed by the channel 22 and the second electrode 26. Therefore, excellent attenuation characteristics are obtained in the same manner as in the LC element 200 of the second embodiment shown in Fig. 14.

Except for the inductance and capacitance values, the equivalent circuit of the LC element 400 is the same as that of the third embodiment shown in Fig. 22. As shown in the figure, the inductance L3 is reduced only to the extent that the number of meander bends of the second electrode 26 is reduced, while the corresponding distributed constant type capacitance C1 is also reduced.

In this way, the channel 22 formed corresponding to the first electrode 10 and the second electrode 26 formed shorter than the first electrode 10 have inductances while a distributed constant type capacitor is formed between them, thereby enabling the LC element 300 to function as an element having excellent attenuation characteristics.

The above description has been made of an LC element 400 in which the channel 22 formed corresponding to the first electrode 10 is used as the signal transmission line. However, it may also be arranged such that the second electrode 26 is used as the signal transmission line and that the channel 22 formed corresponding to the first electrode 10 is connected to ground or a fixed potential.

Fig. 27 shows an example of a variation in which the second electrode 26 is used as the signal transmission line, and it corresponds to Fig. 18 of the second embodiment. In this case, the respective input/output electrodes 18 and 20 are connected to the respective ends of the second electrode 26, while the ground electrode 16 is connected to the source 12 (or drain 14) provided at one end of the channel 22 formed corresponding to the first electrode 10. By forming the first electrode 10 with approximately half the length of the second electrode 26, the channel 22 formed corresponding to the first electrode 10 is also formed with approximately half the length.

Even in this case, the channel 22, which is formed corresponding to the first electrode 10, and the second electrode 26 act accordingly as inductors, while a distributed constant type capacitor is formed between them. Therefore, excellent attenuation characteristics can be obtained as in the LC element 400 shown in Fig. 26.

Fig. 28 shows an example of a variation in which the shortened second electrode 26 is arranged substantially opposite to the first electrode 10 (i.e., the channel 22) on the opposite surface of the p-Si substrate 30, and corresponds to Fig. 26. In order to enable the shape of the back electrode to be seen, the position is slightly shifted to the lower right in Fig. 28. Fig. 29 corresponds to Fig. 27 and shows an example of a variation in which the second electrode 26 is arranged substantially opposite to the first electrode 10 on the opposite surface of the p-Si substrate 30, and the first electrode 10 and the channel 22 formed corresponding thereto are shortened.

As shown in Figs. 28 and 29, even if the meander-shaped channel 22 and the second electrode 26 of different lengths are arranged substantially opposite to each other, the channel 22 and the second electrode 26 function as inductors while a distributed constant type capacitor is formed between them, as in the LC element 400 shown in Fig. 26 and others, thereby providing such advantages as excellent frequency response and ease of manufacture.

The LC element 400 also has the same advantages as the LC elements of the above-described embodiments, such as the ability to be manufactured by using ordinary semiconductor manufacturing technology, the ease of manufacture, and the suitability for size reduction and other requirements. In addition, when the LC element is manufactured as a portion of a semiconductor substrate, the wiring with other components can be carried out simultaneously, in which case the assembly work in subsequent processing becomes unnecessary. In addition, by varying the gate voltage (control voltage) applied to the first elect rode 10, the resistance of the channel 22 and the capacitance of the distributed constant type capacitor formed between the channel 22 and the second electrode 26 can be variably controlled, thereby enabling the overall frequency response of the LC element 400 to be adjusted or changed.

FIFTH EMBODIMENT

The following is a description of an LC element 500 according to a fifth embodiment of this invention with reference to the accompanying drawings.

The foregoing descriptions have referred to LC elements that function as three-terminal normal mode type elements. The LC element 500 of the fifth embodiment is designed to function as a four-terminal common mode type element.

Fig. 30 is a plan view of the LC element 500 according to the fifth embodiment. As shown in the figure, the LC element 500 differs from the LC element 100 shown in Fig. 1 in that the input/output electrodes 36 and 38 are provided at the respective ends of the second electrode 26.

Fig. 31 shows an equivalent circuit of the LC element 500. As shown in the figure, the channel 22 formed between the two input/output electrodes 18 and 20 via the source 12 and the drain 14 functions as an inductor having the inductance L1, and the second electrode 26 formed between the two input/output electrodes 36 and 38 functions as an inductor having the inductance L2. The channel 22 and the second electrode 26 are both used as signal transmission lines, respectively, while a distributed constant type capacitor having a capacitance C is formed therebetween in the same manner as the LC element 100 of the first embodiment.

In this way, in the case of the LC element 500, the functions of a four-terminal common mode type element having excellent attenuation characteristics can be obtained not only by the channel 22 formed corresponding to the first electrode 10 but also by providing the input/output electrodes 36 and 38 at the respective ends of the second electrode 26. In addition, by varying the gate voltage applied to the control electrode 24, the resistance including the above-mentioned inductance having the inductance L1 and the distributed constant type capacitance C can be changed, thereby enabling variable control of the overall attenuation characteristics of the LC element 500.

Fig. 32 shows an example of a variation in which the second electrode 26 is arranged substantially opposite to the first electrode 10 (i.e., the channel 22) on the opposite surface of the p-Si substrate 30. As shown in the figure, even if the spiral channel 22 and the second electrode 26 are arranged substantially opposite to each other, a distributed constant type capacitor is formed between them, and a four-terminal common mode type element having such advantages as excellent frequency response and easy fabrication as in the LC element 500 shown in Fig. 30 can be obtained.

The LC element 500 also has the same advantages as the LC elements of the above-described embodiments, such as the ability to be manufactured by using ordinary semiconductor manufacturing technology, the ease of manufacture, and the suitability for size reduction and other requirements. In addition, when the LC element is manufactured as a portion of a semiconductor substrate, the wiring with the other components can be carried out simultaneously, in which case the assembly work in subsequent processing is unnecessary. In addition, by varying the gate voltage (control voltage) applied to the first electrode 10, the resistance of the channel 22 and the capacitance of the distributed constant type capacitor formed between the channel 22 and the second electrode 26 can be variably controlled, thereby enabling the overall frequency response of the LC element 500 to be adjusted or changed.

SIXTH EMBODIMENT

The following is a description of an LC element 600 according to a sixth embodiment of this invention with reference to the accompanying drawings.

An LC element according to the sixth embodiment differs from the fifth embodiment mainly by using non-spiral shapes for the first electrode 10 and the second electrode 26. Of course, the channel 22 formed along the first electrode 10 is also of a non-spiral shape. In the figures, the same designations are used for items corresponding to those of the fifth embodiment.

The foregoing descriptions of the LC elements 100, 200, 300 and 400 of the respective first to fourth embodiments refer to LC elements that function as three-terminal normal mode type elements. The LC element 600 of the sixth embodiment is designed to function as a four-terminal common mode type element.

Fig. 33 is a plan view of the LC element 600 according to the sixth embodiment. As shown in the figure, the LC element 600 differs from the LC element 200 shown in Fig. 14 in that the input/output electrodes 36 and 38 are provided at the respective ends of the second electrode 26.

Except for the inductance and capacitance values, an equivalent circuit of the LC element 600 is the same as that of the fifth embodiment shown in Fig. 31. As shown in the figure, the channel 22 formed between the two input/output electrodes 18 and 20 via the source 12 and the drain 14 functions as an inductor having the inductance L1, and the second electrode 26 formed between the two input/output electrodes 36 and 38 functions as an inductor having the inductance L2. Both the channel 22 and the second electrode 26 are respectively used as signal transmission lines, while a distributed constant type capacitor having the capacitance C is formed therebetween in the same manner as the LC element 100 of the first embodiment.

In this way, in the case of the LC element 600, not only by the channel 22 formed corresponding to the first electrode 10 but also by providing the input/output electrodes 36 and 38 at the respective ends of the second electrode 26, the functions of a four-terminal common mode type element having excellent attenuation characteristics can be obtained. In addition, by varying the gate voltage applied to the control electrode 24, the resistance included in the above-mentioned inductance having the inductance L1 and the distributed constant type capacitance C can be changed, thereby enabling variable control of the overall attenuation characteristics of the LC element 600.

Fig. 34 shows an example of a variation in which the second electrode 26 is formed substantially opposite to the first electrode 10 (ie, the channel 22) on the opposite surface of the p-Si substrate 30. As shown in the figure, even if the meander-shaped channel 22 and the second electrode 26 are arranged substantially opposite to each other, a distributed constant type capacitor is formed between them in the same manner as in the LC element 600 shown in Fig. 33, and a four-terminal common mode type element which such advantages as excellent frequency response and ease of manufacturing can be obtained.

The LC element 600 also has the same advantages as the LC elements of the above-described embodiments, such as the ability to be manufactured by using ordinary semiconductor manufacturing technology, the ease of manufacture, and the suitability for size reduction and other requirements. In addition, when the LC element is manufactured as a portion of a semiconductor substrate, the wiring with other components can be carried out simultaneously, in which case the assembly work in subsequent processing is unnecessary. In addition, by varying the gate voltage (control voltage) applied to the first electrode 10, the resistance of the channel 22 and the capacitance of the distributed constant type capacitor formed between the channel 22 and the second electrode 26 can be variably controlled, thereby enabling the overall frequency response of the LC element 600 to be adjusted or changed.

SEVENTH EMBODIMENT

The following is a description of an LC element according to a seventh embodiment of this invention with reference to the accompanying drawings.

In the respective LC elements of the above-described embodiments, the second electrode 26 comprises a single conductor. In the case of the LC element 700 of the seventh embodiment, the second electrode 26 comprises a plurality (for example, two) of divided electrode segments 26-1 and 26-2.

Fig. 35 is a plan view of the LC element 700. As shown in the figure, the LC element 700 is constructed such that the second electrode 26 used for the LC element 100 shown in Fig. 1 is replaced by divided electrode segments 26-1 and 26-2. These divided electrode segments 26-1 and 26-2, which as a whole form a spiral shape are connected to ground electrodes 16, respectively. By grounding the two ground electrodes 16, the inductances formed by the two divided electrode segments 26-1 and 26-2, respectively, are grounded. Alternatively, by connecting the two ground electrodes 16 to a power supply with a fixed potential, the portions of the inductances formed by the two divided electrode segments 26-1 and 26-2, respectively, are fixed at this potential.

Fig. 36 shows an equivalent circuit of the LC element 700. As shown in the figure, the channel 22 formed corresponding to the first electrode 10 acts as an inductor having a total inductance L1, while the divided electrode segments 26-1 and 26-2 act as inductors having the inductances L3 and L4, respectively. In addition, the channel 22 and the corresponding divided electrode segments 26-1 and 26-2 act as distributed constant type capacitors having the capacitances C2 and C3.

The self-inductances of the divided electrode segments 26-1 and 26-2 are small and their influence on the overall characteristics of the LC element 700 is similarly small. As a result, the overall characteristics of the LC element 700 are largely determined by the channel 22 formed corresponding to the first electrode 10 having the inductance L1 and the distributed constant type capacitances C2 and C3.

The plan view of Fig. 35 shows the case where the channel 22 formed corresponding to the first electrode 10 is used as the signal transmission line and the second electrode 26 is divided into two segments. However, the opposite construction may also be used in which the second electrode 26 is used as the signal transmission line and the first electrode 10 is divided into plural. In this case, since the channel 22 is also formed into plural parts in corresponding correspondence to the plurality of divided first electrodes 10, a source 12 or drain 14 near one end of each channel and ground electrodes 16 connected thereto may be provided.

Fig. 37 shows an example of a variation in which the two divided electrode segments 26-1 and 26-2 of the first electrode 10 are arranged substantially opposite to each other on the opposite side of the p-Si substrate 30. As shown in the figure, even if the spiral channel 22 and the two divided electrode segments 26-1 and 26-2 are arranged substantially opposite to each other, the channel 22 and the divided electrode segments 26-1 and 26-2 respectively function as inductors in the same manner as in the LC element 700 shown in Fig. 35 while a distributed constant type capacitor is formed between them, thereby providing such advantages as excellent frequency response and ease of manufacture.

The LC element 700 also has the same advantages as the LC elements of the above-described embodiments, such as the ability to be manufactured by using ordinary semiconductor manufacturing technology, the ease of manufacture, and the suitability for size reduction and other requirements. In addition, when the LC element is manufactured as a section of a semiconductor substrate, the wiring with other components can be carried out simultaneously, in which case the assembly work in subsequent processing becomes unnecessary. In addition, by varying the gate voltage (S control voltage) applied to the first electrode 10, the resistance of the channel 22 and the capacitance of the distributed constant type capacitor formed between the channel 22 and the divided electrode segments 26-1 and 26-2 can be variably controlled, thereby enabling the overall frequency response of the LC element 700 to be adjusted or changed.

EIGHTH EMBODIMENT

The following is a description of an LC element according to an eighth embodiment of this invention with reference to the accompanying drawings.

In the respective LC elements of the first to sixth embodiments described above, the second electrode 26 has a single conductor. In the case of the LC element 800 of the eighth embodiment, the second electrode 26 has a plurality (for example, two) of divided electrode segments 26-1 and 26-2.

Fig. 38 is a plan view of the LC element 800. As shown in the figure, the LC element 800 is constructed such that the second electrode 26 used for the LC element 200 shown in Fig. 14 is replaced by divided electrode segments 26-1 and 26-2. These divided electrode segments 26-1 and 26-2, which have a meander shape as a whole, are connected to ground electrodes 16, respectively. By grounding the two ground electrodes 16, the inductors formed by the two divided electrode segments 26-1 and 26-2, respectively, are grounded. Alternatively, by connecting the two ground electrodes 16 to a power supply with a fixed potential, the sections of the inductances, which are formed by the two divided electrode segments 26-1 and 26-2, can be fixed at this potential.

Except for the inductance and capacitance values, the equivalent circuit of the LC element 800 is the same as that of the seventh embodiment shown in Fig. 36. As shown in the figure, the channel 22 formed corresponding to the first electrode 10 acts as an inductor having a total inductance L1, while the divided electrode segments 26-1 and 26-2 act as inductors having the inductances L3 and L4, respectively. In addition, the channel 22 and the corresponding divided electrode segments 26-1 and 26-2 act as distributed constant type capacitors having capacitances C2 and C3.

The self-inductances of the divided electrode segments 26-1 and 26-2 are small and their influence on the overall characteristics of the LC element 800 is similarly small. As a result, the overall characteristics of the LC element 800 are largely determined by the channel 22 formed corresponding to the first electrode 10 having the inductance L1 and the distributed constant type capacitances C2 and C3.

The plan view of Fig. 38 shows the case where the channel 22 formed corresponding to the first electrode 10 is used as the signal transmission line, and the second electrode 26 is divided into two segments. However, the opposite construction can also be used where the second electrode 26 is used as the signal transmission line and the first electrode 10 is divided into several. In this case, since the channel 22 is also formed in a plurality of parts in respective correspondence to the plurality of divided first electrodes 10, a source 12 or a drain 14 near one end of each channel and ground electrodes 16 connected to them can be provided.

Fig. 39 shows an example of a variation in which two divided electrode segments 26-1 and 26-2 of the first electrode 10 are arranged substantially opposite to each other on the opposite side of the p-Si substrate 30. As shown in the figure, even if the meander-shaped channel 22 and the two divided electrode segments 26-1 and 26-2 are arranged substantially opposite to each other, the channel 22 and the divided electrode segments 26-1 and 26-2 respectively function as inductors in the same manner as in the LC element 800 shown in Fig. 38 while a distributed constant type capacitor is formed between them, thereby providing such advantages as excellent frequency response and ease of manufacturing.

The LC element 800 also has the same advantages as the LC elements of the embodiments described above, such as the ability to use conventional Semiconductor manufacturing technology, ease of manufacture and suitability for size reduction and other requirements. In addition, when the LC element is manufactured as a section of a semiconductor substrate, wiring with other components can be carried out simultaneously, in which case assembly work in subsequent processing is unnecessary. In addition, by varying the gate voltage (control voltage) applied to the first electrode 10, the resistance of the channel 22 and the capacitance of the distributed constant type capacitor formed between the channel 22 and the divided electrode segments 26-1 and 26-2 can be variably controlled, thereby enabling the overall frequency response of the LC element 800 to be adjusted or changed.

NINTH EMBODIMENT

The following is a description of LC elements according to a ninth embodiment of this invention with reference to the accompanying drawings.

In general, the function as an inductor having a predetermined inductance is obtained by forming a conductor in a spiral/coil shape. As mentioned above, a channel 22 and a second electrode 26 of meander shapes also function as inductors having predetermined inductances. However, when the input signal is limited to a high frequency band, shapes other than spiral or meander shapes and, in extreme cases, even straight line shapes function as inductors having inductance components. In view of these factors, the LC elements according to the present embodiment have a channel 22 formed corresponding to the first electrode 10 and a second electrode 26 formed in shapes other than spiral shapes.

Figs. 40A, 40B, 41A and 41B are plan views of LC elements in which the channel 22 formed corresponding to the first electrode 10 and the second electrode 26 have straight line shapes, respectively.

Fig. 40A corresponds to Fig. 1 and shows a three-terminal type LC element in which the channel 22 and the second electrode 26 are formed with substantially the same length and substantially parallel.

Fig. 40B corresponds to Fig. 21 and shows an LC element in which the second electrode 26 is provided corresponding to a portion of the channel 22 which is formed corresponding to the first electrode 10.

Fig. 41A corresponds to Fig. 30 and shows a four-terminal common mode type element in which the input/output electrodes 36 and 38 are provided at the respective ends of the second electrode 26.

Fig. 41B corresponds to Fig. 35 and shows an LC element in which the second electrode 26 is divided into two divided electrode segments 26-1 and 26-2.

Although Figs. 40A, 40B, 41A and 41B show LC elements in which the first electrode 10 and the second electrode 26 are formed in substantially the same plane, as shown in Figs. 11, 12 and others, the first electrode 10 and the second electrode 26 may also be arranged in a substantially opposing manner on opposite sides of the p-Si substrate 30.

Fig. 42 is a plan view of an LC element in which the second electrode 26 and the channel 22 formed corresponding to the first electrode 10 have curved line shapes with a large radius of curvature. Curved line shapes shown in the figure can be used for the first electrode 10 and the second electrode 26 in such situations when other components are arranged at the positions of a straight line connecting the two input/output electrodes 18 and 20.

Fig. 43 is a plan view of an LC element in which the channel 22 formed corresponding to the first electrode 10 and the second electrode 26 have waveforms. Although not to the extent of the spiral shapes shown in Figs. 1 and others, this LC element has a larger inductance compared to the straight or large curved line shapes for the channel 22 and the second electrode 26.

Fig. 44 is a plan view of an LC element in which the second electrode 26 and the channel 22 formed corresponding to the first electrode 10 are formed in incomplete circular shapes. As shown in the figure, by forming the channel 22 and the second electrode 26 in incomplete circular shapes, an LC element having a small inductance can be obtained. Also, by folding back one or both ends of the first electrode 10 (channel 22) and the second electrode 26, the generated magnetic flux can be partially cancelled to reduce the inductance. As a result, the total inductance, i.e., the frequency response of the LC element, can be adjusted.

To simplify the description, only the examples corresponding to the LC element shown in Fig. 40A are shown in Figs. 42 to 44. However, the same concepts can also be applied to the LC element types shown in Figs. 40B, 41A and 41B, as well as to the types in which the first electrode 10 and the second electrode 26 are arranged substantially opposite to each other on opposite sides of the p-Si substrate 30.

In this way, the LC elements shown in Figs. 40A to 44 have neither spiral nor meander shapes for the first electrode 10, the channel 22 formed corresponding thereto and the second electrode 26. As a result, In addition, the same advantages as the LC elements of the above-described embodiments, such as the ability to be manufactured by using ordinary semiconductor manufacturing technology, the ease of manufacture, and the suitability for size reduction and other requirements, are obtained. In addition, when the LC element is manufactured as a portion of a semiconductor substrate, the wiring with other components can be carried out simultaneously, in which case the assembly work in subsequent processing becomes unnecessary. In addition, by varying the gate voltage applied to the first electrode 10, the resistance of the channel 22 and the capacitance of the formed distributed constant type capacitor can be controlled, thereby enabling the overall characteristics of the LC elements to be variably controlled.

OTHER EMBODIMENTS

The following is a description of other embodiments of this invention with reference to the accompanying drawings.

In the embodiments described above, the two input/output electrodes 18 and 20 are arranged at separate positions near the respective ends of the first electrode 10. However, the shape of the first electrode 10 can be modified to allow close positioning of the input/output electrodes 18 and 20.

For example, in the case of meander-shaped or other shaped electrodes shown in Fig. 45, the source 12 and the drain 14 are arranged adjacently, while one end of each of the first and second electrodes 10 and 26 shown in Fig. 14 is extended to the drain 14. Alternatively, as shown in Fig. 46, the source 12 and the drain 14 are arranged adjacently, and the first and second Electrodes 10 and 26, shown in Fig. 14, are folded back in a manner that maintains their meander shape.

In this way, by modifying the shape of the first electrode 10 (or both the first and second electrodes 10 and 26), the two input/output electrodes 18 and 20 are positioned close to each other, and the ground electrode 16, the control electrode 24, and the input/output electrodes 18 and 20 can all be formed at almost the same position. As a result, the wiring can be easily carried out when the terminals are connected, and the manufacturing processes can be shortened.

Figs. 47 and 48 are descriptive drawings showing the provision of the terminals by such methods as chemical liquid phase deposition. Fig. 47 is a plan view of an LC element corresponding to Fig. 1 and others. As shown in the figure, the control electrode 24 and the ground electrode 16 are not provided for the first electrode 10 and the second electrode 26.

After separating the individual LC elements from a semiconductor substrate containing the first and second electrodes 10 and 26 having this type of shape, a silicon oxide layer 40 is formed as an insulating layer on the entire surface of the separated chips (elements) by chemical liquid phase deposition. Openings are then opened by etching to remove the silicon oxide layer 40, respectively, over one end of the first and second electrodes 10 and 26. The openings are closed by applying solder 42 to the extent that it protrudes slightly above the surface, thereby allowing the protruding solder 42 to contact such structures as the terminals of printed circuit boards. In the following, preferred conditions for surface mounting are provided. Fig. 48 is a cross-sectional view of a chip (element) subjected to this type of processing, viewed along line E-E in Fig. 47.

Synthetic resin or other insulating material may be used for the surface protective layer of the element, and laser light is used to perforate the protective layer. As shown in Fig. 48, by setting the layer thickness for each electrode so that the input/output electrodes 18 and 20 and the first and second electrodes 10 and 26, etc. have the same height, since the height of the projecting solder 42 becomes almost the same, the conditions for surface mounting are very favorable. In addition, as shown in Figs. 11, 12A and others, in cases where the second electrode 26 is arranged substantially opposite to the first electrode 10, by using through holes so that the wiring is on one side and applying solder 42 so that it projects in the same way, the wiring and other work in subsequent processing are made easy.

Fig. 49 is a descriptive drawing for describing the formation of the LC elements 100 and others of the foregoing embodiments as portions of an LSI or other device. As shown in the figure, the LC elements 100 are inserted into the signal or power supply lines 48 on the semiconductor chip 46. Particularly, since the LC elements 100 etc. of the foregoing embodiments can be manufactured simultaneously with the formation of the other circuits on the semiconductor chip 46, work such as wiring in subsequent processing steps becomes unnecessary.

In Fig. 49 and Figs. 50A to 50E mentioned below, although the LC element 100 of the first embodiment is shown as a representative, the LC element may be replaced by any of the LC elements of the other embodiments such as the LC element 300.

In general, the channel 22 having an inductance has a high resistance in, for example, the LC element 100. In addition, since the total length of this channel 22 is long, a signal level attenuation is generated between the two input/output Electrodes 18 and 20. For this reason, when the LC element 100 and others are used as a portion of an actual circuit, a more practical construction is to connect a buffer with high input impedance to the output side.

50A to 50E show examples of a buffer connection to the output side of the LC element 100 of the first embodiment.

Fig. 50A shows the use of a source follower circuit 50 comprising a MOSFET and a resistor as a buffer. Since the MOSFET has the same construction as any of the LC elements of the above-mentioned embodiments, the entire LC element including the source follower circuit 50 can be easily formed in an integrated manner.

Fig. 50B shows the use of an emitter follower circuit 52 comprising two bipolar transistors in a Darlington connection and a resistor as a buffer. Since the construction of the bipolar transistor differs only slightly from the construction of the LC elements of the above-mentioned embodiments, the entire LC element including the emitter follower circuit 52 can be formed in an integrated manner on the same semiconductor substrate. In addition, by grounding the ground of the transistor closer to the output through a resistor, the operating point of the transistor can be further stabilized.

Fig. 50C shows an example of a circuit having a p-channel MOSFET used as a buffer with reverse bias.

Fig. 50D shows an example of an amplifier circuit 54 comprising two MOSFETs and resistors used as a buffer. Since the MOSFET construction is the same as the construction of the LC elements of the above-mentioned embodiments, the entire LC element comprising the amplifier circuit 54 can be formed uniformly on the same semiconductor substrate. The voltage amplification factor of this circuit is 1 + (R2/R1) and by setting R2 = 0, the circuit is equivalent to a source follower.

Fig. 50E shows an example of an amplifier circuit 55 comprising two bipolar transistors and resistors used as a buffer. Since the construction of the bipolar transistors differs only slightly from the construction of the LC elements of the above-mentioned embodiments, the entire LC element including the amplifier circuit 55 can be formed in an integrated manner on the same semiconductor substrate. The voltage amplification factor of this circuit is 1 + (R2/R1), and by setting R2 = 0, the circuit is equivalent to an emitter follower.

In cases where the LC element 100 shown in Figs. 50A to 50E is replaced by a common mode type LC element, for example, an LC element 500 of the fifth embodiment, since both the channel 22 and the second electrode 26 are used as signal transmission lines, an above-mentioned buffer circuit 50, 52, 53, 54, 55 is also connected to the output side of the second electrode 26.

In this way, by providing a buffer on the output side, the signal level attenuated by the inductance section (channel 22) can be restored, and an output signal with an excellent SN ratio can be obtained.

In addition, by connecting a level converter circuit to the output side of the LC element 100, etc., amplification of the signal level attenuated by the inductance portion, conversion to a predetermined level, or level correction can be easily performed. Like the buffers mentioned above, these level converter circuits can be formed in an integrated manner with the LC elements of the above-described embodiments on the same substrate.

In addition, a voltage controlled oscillator (VCO) can be constructed using the LC elements 100 and others of any of the above-mentioned embodiments. By changing an externally applied gate voltage to the control electrode 24, i.e., by changing the capacitance of the distributed constant type capacitor and the resistance of the channel 22, the VCO oscillation frequency can be changed as desired within a certain range.

51A and 51B show examples of adding input protection circuits to the LC elements of the above embodiments. Due to their MOS construction, a high voltage applied to the control electrode 24 due to static electricity may destroy the insulation layer 28 between the first electrode 10 and the p-Si substrate 30. Therefore, a protection circuit is needed to prevent destruction of the insulation layer 28 by static electricity.

The protection circuits shown in the figures both comprise a plurality of diodes and resistors. When a high voltage is applied to the second electrode 26 connected to the first electrode 10, the current is diverted to the operating power line or the chassis ground. The circuit of Fig. 51A can withstand several hundred volts, while the circuit of Fig. 51B can withstand 1000 to 2000 volts. The appropriate protection circuit can be selected according to the use environment and other factors.

The foregoing descriptions of the embodiments do not limit this invention, and numerous variations are possible within the scope of the invention.

For example, the above descriptions referred to enhancement-type LC elements in which the channel 22 is formed when a predetermined gate voltage is applied to the control electrode 24. However, depletion-type LC elements can also be formed. In other words, charge carriers (n-type dopants) are previously injected into the region of the channel 22 shown in Fig. 1 and others. As a result, the channel 22 may be formed in the state without an applied gate voltage, or the relationship between the applied gate voltage and the channel width, etc. may be changed. In addition, carriers (n-type dopants) may be injected only partially along the region of the first electrode, and the first electrode corresponding to the injected carriers may be completely or partially omitted.

Furthermore, in the above-mentioned embodiments, the second electrode 26 directly contacts the p-Si substrate 30 while the first electrode 10 is formed over the insulating layer 28. However, the opposite is also possible, namely, forming the first electrode 10 in direct contact with the p-Si substrate 30 and the second electrode 26 over the insulating layer 28. It is also possible to form both the first and second electrodes 10 and 26 on the surface of the insulating layer 28.

Furthermore, in the above-described embodiments in which the first and second electrodes 10 and 26 were formed in substantially the same surface, the first electrode 10 was formed over the insulating layer 28 and the first and second electrodes, etc. were formed on a p-Si substrate 30 having a single p-layer. However, by forming an inversion layer that is spiral-shaped, etc., along these electrodes, secure isolation/separation can be provided between adjacent portions of the channel 22.

52A and 52B correspond to FIGS. 2A and 2B and show cross-sectional views of the formation of a substantially spiral inversion layer 66 along the first and second electrodes 10 and 26. As shown in FIG. 52A, the inversion layer 66 having a spiral p-type region is formed corresponding to the first and second electrodes 10 and 26 in a portion of a substrate 64 having an n-type region. In the case of an LC element having this type of construction, when a predetermined gate voltage is applied to the control electrode 24 connected to the first electrode 10, the channel 22 is formed near the surface corresponding to the first electrode 10 as shown in Fig. 52B. In addition, by applying a reverse bias to the substrate 64 and the spiral inversion layer 66, they can be electrically separated from each other, thereby securely forming a distributed constant type capacitor between the channel 22 and the second electrode 26.

Furthermore, considering the LC elements of the above-mentioned embodiments in which the first and second electrodes 10 and 26 are arranged substantially opposite to each other, although the first and second electrodes 10 and 26, etc. are formed on a p-Si substrate 30 having a single p-region, by forming an inversion layer between adjacent portions of the first electrode 10 or the second electrode 26, separation can be securely obtained between adjacent portions of the channel 22.

Fig. 53 corresponds to Fig. 12 and shows a cross-sectional construction in which inversion layers are formed between the first electrode 10 and the second electrode 26. As shown in the figure, the inversion layers comprise n-type regions 74 formed in portions of the p-Si substrate 30. In the case of an LC element having this type of construction, since the n-type regions 74 are formed between the portions of the p-Si substrate 30 connected to adjacent portions of the second electrode 26, they are electrically separated and secure insulation can be obtained.

In addition, when an LC element in which the first and second electrodes 10 and 26 are substantially opposed to each other is manufactured using an actual wafer-shaped p-Si substrate 30, since the resistance of the p-Si substrate 30 is comparatively higher than that of a metallic material, the thickness of the p-Si substrate 30 does not have to be thinner than the wafer shape. In addition, since the n-type wafer are generally easier to obtain, the construction as shown in Figs. 54A and 54B may be used.

As shown in Fig. 54A, etching is performed, for example, in a spiral shape on a surface of an n-Si substrate 76, and the first or second electrode 10 or 26 is formed in this etched portion. In addition, as shown in Fig. 54B, a p+ region 78 is formed substantially along the respective first and second electrodes 10 and 26 in a portion of the n-Si substrate 76. Etching is then performed in the portion corresponding to the second electrode 26 on the back surface of the n-Si substrate 76. Finally, the first and second electrodes 10 and 26 are formed.

Also with respect to this embodiment, the ability to form the LC element 100, etc. as a portion of an LSI or other device has been mentioned, but the formation as a portion of an LSI or other device is not essential. After forming the LC element 100 on the semiconductor substrate, providing respective terminals for the input/output electrodes 18 and 20, the ground electrode 16 and the control electrode 24 or providing terminals by chemical liquid phase deposition as shown in Figs. 47 and 48, the formation as a discrete element is also acceptable. In this case, by simultaneously forming a plurality of LC elements on the same semiconductor substrate, subsequently cutting the semiconductor substrate and providing the terminals on the LC elements, easy mass production is enabled.

Also in the embodiments described above, the ground electrode 16, the source 12 and the drain 14 were provided at the endmost portions of the first and second electrodes 10 and 26. However, it is not essential that they be provided at the absolute ends, and the mounting positions may be shifted according to the requirements after a frequency response study.

Also in the LC elements of the above-described embodiments, by changing the gate voltage applied to the control electrode 24, the resistance of the channel 22 and the capacitance of the distributed constant type capacitor are changed, thereby making variable control of the overall frequency response of the LC element possible. As a result, by using the LC element 100 and others as a circuit section, variable frequency type circuits such as tuners, modulators, oscillators and filters can be easily constructed.

Furthermore, in the embodiments described above, the example of forming a pn junction layer 26 on a p-Si substrate 30 was given. However, other types of semiconductors such as germanium or non-crystalline materials such as amorphous silicon may also be used.

Translation of the text in Fig. 9G:

p-glass = P-Glas

Claims (30)

1. LC element which has: either an n-type or a p-type semiconductor substrate (30), a first electrode (10) functioning as a gate having a predetermined shape formed on an insulating layer (28) on the semiconductor substrate (30), a second electrode (26) having a predetermined shape formed on the semiconductor substrate (30) adjacent to, substantially parallel to and on the same substrate side as the first electrode (10), a first diffusion region (12) formed near an end of a channel (22) which is present at least in use and corresponding to the first electrode (10) in the semiconductor substrate (30), and a second diffusion region (14) formed near the other end of the channel (22) in the semiconductor substrate (30), in which the channel (22) and the second electrode (26) form respective inductors, thereby forming a distributed constant type capacitor therebetween, and at least the channel formed corresponding to the first electrode (10) is used as a signal transmission line. 2. LC element that has: a first electrode (10) having a predetermined shape functioning as a gate formed on an insulating layer (28) on one side of a semiconductor substrate (30), a second electrode (26) having a predetermined shape formed on the opposite side of the semiconductor substrate (30) in a position substantially opposite to the first electrode, a first diffusion region (12) formed near an end of a channel (22) which is present at least in use and is formed in the semiconductor substrate corresponding to the first electrode (10), and a second diffusion region (14) formed near the other end of the channel in the semiconductor substrate, in which the channel (22) and the second electrode (26) form inductors respectively, thereby forming a distributed constant type capacitor therebetween, and at least the channel (22) formed corresponding to the first electrode is used as a signal transmission line. 3. The LC element according to claim 1, wherein the semiconductor substrate (30) has an inversion layer having either an n- region or a p-region formed along the first and second electrodes. 4. LC element according to claim 2, wherein the semiconductor substrate (30) has an inversion layer having either an n- region or a p-region formed between adjacent portions of the first and second electrodes (10, 26). 5. LC element according to one of claims 1-4, wherein the first and second electrodes (10, 26) have spiral shapes. 6. LC element according to one of claims 1-4, wherein the first and second electrodes (10, 26) have meandering shapes. 7. LC element according to one of claims 1-4, wherein the first and second electrodes (10, 26) have curved line shapes. 8. LC element according to one of claims 1-4, wherein the first and second electrodes (10, 26) have straight line shapes. 9. LC element according to one of claims 1-8, further comprising: first and second input/output electrodes (18, 20) electrically connected to the first and second diffusion regions (12, 14) respectively, and a ground electrode (16) electrically connected near one end of the second electrode (26), wherein a signal of one electrode is input from the first and second input/output electrodes and an output signal is obtained from the other electrode from these first and second input/output electrodes, and the ground electrode (16) is connected to a power supply at a fixed potential or is grounded. 10. LC element according to one of claims 1-8, further comprising: first and second input/output electrodes (18, 20) electrically connected to the first and second diffusion regions (12, 14) respectively, and a third and a fourth input/output electrode (36, 38) which are electrically connected to one end or the other end of the second electrode (26) in which both the channel (22) formed corresponding to the first electrode and the second electrode are used as signal transmission lines and enable use as a common mode element. 11. LC element according to one of claims 1-9, wherein only the channel (22) is used as a signal transmission line, the second electrode (26) is divided into a plurality of segments, and the correspondingly divided plurality of electrode segments are mutually electrically connected. 12. LC element which has: either an n-type or a p-type semiconductor substrate (30), a first electrode (10) functioning as a gate having a predetermined shape formed on an insulating layer (28) on the semiconductor substrate, a second electrode (26) having a predetermined shape formed on the semiconductor substrate (30) adjacent to, substantially parallel to and on the same substrate side as the first electrode (10), and a diffusion region (12) formed near an end of a channel (22) which is present at least in use and is formed in the semiconductor substrate (30) corresponding to the first electrode (10), in which the channel (22) and the second electrode (26) form corresponding inductors, whereby a distributed constant type capacitor is formed therebetween, and the second electrode (26) is used as a signal transmission line. 13. LC element comprising: a first electrode (10) functioning as a gate having a predetermined shape formed on an insulating layer (28) on a semiconductor substrate (30), a second electrode (26) having a predetermined shape formed on the opposite side of the semiconductor substrate (30) in a position substantially opposite to the first electrode (10), and a diffusion region (12) formed near an end of a channel (22) which is present at least in use and corresponding to the first electrode (10) in the semiconductor substrate (30), in which the channel (22) and the second electrode (26) form inductors respectively, thereby forming a distributed constant type capacitor therebetween, and the second electrode (26) is used as a signal transmission line. 14. The LC element according to claim 12, wherein the semiconductor substrate (30) has an inversion layer having an n-type region or a p-type region formed along the first and second electrodes (10, 26). 15. The LC element according to claim 13, wherein the semiconductor substrate (30) has an inversion layer having either an n- region or a p-region formed between adjacent portions of the first and second electrodes (10, 26). 16. LC element according to one of claims 12-15, wherein the first and second electrodes (10, 26) have spiral shapes. 17. LC element according to one of claims 12-15, wherein the first and second electrodes (10, 26) have meandering shapes. 18. LC element according to one of claims 12-15, in which the first and second electrodes (10, 26) have curved line shapes. 19. LC element according to one of claims 12-15, wherein the first and second electrodes (10, 26) have straight line shapes. 20. LC element according to one of claims 12-19, further comprising: first and second input/output electrodes (36, 38) electrically connected to one end or the other end of the second electrode (26) respectively, and a ground electrode (16) electrically connected to the diffusion region formed near an end of the channel formed corresponding to either the first electrode or the first electrode divided into electrode segments, in which a signal of either the first or the second input/output electrode is inputted and an output signal is obtained from the other of the first and second input/output electrodes, and the ground electrode (16) is connected to a power supply with fixed potential or is connected to ground. 21. An LC element according to any one of claims 12-20, wherein the first electrode (10) is divided into a plurality of segments, diffusion regions are provided near an end of each of a plurality of channels formed in correspondence to the respective plurality of divided electrode segments, and the plurality of diffusion regions are electrically connected. 22. LC element according to one of claims 1-21, in which by variably adjusting a gate voltage applied with respect to the first electrode, at least the channel resistance is variably controlled. 23. LC element according to one of claims 1-22, in which charge carriers are previously injected into a position corresponding to the first electrode (10) near the surface of the semiconductor substrate (30). 24. LC element according to one of claims 1-23, in which by setting the length of the second electrode (26) longer or shorter with respect to the first electrode (10), a section-wise correspondence between the channel (22) and the second electrode (26) is created. 25. LC element according to one of claims 1-24, wherein a buffer (55) is connected to the output side of the signal transmission line. 26. LC element according to one of claims 1-25, wherein a protection circuit is provided whereby at least an excessive voltage in the first electrode is diverted to the operating power supply line or to ground. 27. An LC element according to any one of claims 1-26, wherein terminals are provided by forming an insulating layer on the entire surface, opening perforations in portions of the insulating layers by etching or laser light emission, and closing the perforations by applying solder (42) to an extent of slightly protruding from the surface. 28. A semiconductor device formed in an integrated manner in which an LC element according to any one of claims 1-27 is formed as a portion of a semiconductor substrate (30), and at least one of the channels (22) formed corresponding to the first electrode or the second electrode is inserted into a signal line or a power supply line. 29. A method for producing an LC element suitable for producing an LC element according to claim 1 or 2, comprising the steps: a first process by which first and second diffusion regions (12, 14) are formed by injecting dopant into a semiconductor substrate (30) in sections, a second process by which an insulating layer (28) is formed on the entire surface of or in sections on the semiconductor substrate (30), a spiral or meander-shaped first electrode (10) is formed on the insulating layer (28) so as to couple the first and second diffusion regions, and a spiral or meander-shaped second electrode (26) in an adjacent position, is formed substantially parallel to and substantially along the first electrode (10), and a third process by which wiring layers are formed in electrical connection with the first and second diffusion regions (12, 14) and the first and second electrodes (10, 26), respectively. 30. A method for producing an LC element suitable for producing an LC element according to claim 12 or 13, comprising the steps of: a first process by which a diffusion region (12, 14, 22) is formed by injecting dopant in sections into a semiconductor substrate (30), a second process by which an insulating layer (28) is formed on the entire surface of or in sections on the semiconductor substrate (30), a spiral or meander-shaped first electrode (10) is formed on the insulating layer (28) in a manner by which one end is positioned near the diffusion region, and a spiral or meander-shaped second electrode (26) is formed in an adjacent position, substantially parallel to and substantially along the first electrode, and a third process by which a wiring layer is formed in electrical connection with the diffusion region (12, 14, 22) and the first and second electrodes (10, 26), respectively.