JPH09321312A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the production yield of a thin film transistor having a light doped drain(LDD) region. SOLUTION: An anodic oxidation film 305 having a compact structure is formed on the surface of an Al film 304 and wet etched, using a resist mask 300. This results in a horizontal etching proceeding as shown by a distance 308 and the film 305 having a compact structure remains extruding from a pattern. The extruded film 307 is removed before etching a silicon oxide film 303. This avoids the influence of the etching of the silicon oxide film 303.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD [0001] The invention disclosed in the present specification is:
The present invention relates to a thin film transistor manufacturing process.

[0002]

2. Description of the Related Art A thin film transistor formed on a glass substrate or a quartz substrate is known. It is considered that the thin film transistor is used in an active matrix type liquid crystal device and various semiconductor integrated circuits.

In general, a thin film transistor has a problem that its crystallinity is incomplete, so that it is significantly deteriorated and the OFF current value is large.

These problems are caused by a strong electric field near the boundary between the source / drain region (particularly the drain region) and the channel formation region. Therefore, a configuration is known in which the above-mentioned problems are solved by relaxing this strong electric field.

As such a structure, a structure in which an LDD (lightly doped drain) region and an offset gate region are arranged is known.

As a method of forming the LDD region in a self-aligned manner, the structure described in Japanese Patent Laid-Open No. 169974/1995 is known.

FIG. 3 shows a manufacturing process of the thin film transistor in which the LDD region described in the above publication is arranged. First, a thickness of 100 is formed as a base oxide film 102 on a glass substrate 101.
A silicon oxide film of 0 to 3000 Å is formed.

Next, an amorphous silicon film is formed to a thickness of 500Å by plasma CVD method or LPCVD method. Then, the amorphous silicon film is transformed into a crystalline silicon film by heat treatment or laser light irradiation.

By patterning the obtained crystalline silicon film, an active layer of a thin film transistor is formed. Further, the thickness is 700 to 1500 by the sputtering method.
A Å silicon oxide film 104 is formed.

Next, an aluminum film (not shown) is formed on the silicon oxide film 104 by a sputtering method. Further, a dense ultrathin anodic oxide film (not shown) is formed. This anodic oxide film has the effect of enhancing the adhesiveness of the resist mask to be arranged later.

Then, a resist mask 106 is arranged and the aluminum film is patterned. In this way, the pattern 105 serving as the base of the gate electrode is formed. Thus, the state shown in FIG. 3A is obtained.

Next, the pattern 103 made of aluminum is anodized by passing an electric current in an electrolytic solution. 5 in this step
A 000Å anodic oxide 107 is formed. This anodic oxide (which is not appropriate to call a film) has a porous film quality. Thus, the state shown in FIG. 3B is obtained.

After that, the silicon oxide film 104 is etched by a dry etching method. Then, the resist mask 106 is removed. Thus, the state shown in FIG. 3C is obtained. In this state, the remaining silicon oxide film is denoted by 104 '.

Next, an electric current is applied to the gate electrode again in the electrolytic solution. This step is performed under the condition that an anodic oxide film having a dense film quality is formed. As a result, an anodized film 108 having a dense film quality is formed.

In this step, since the electrolytic solution penetrates into the porous anodic oxide 107, an anodized film having a dense film quality is formed in the state shown by 108. Thus, the state as shown in FIG. 3D is obtained.

Next, the porous anodic oxide 107 is removed. Then, P (phosphorus) ion implantation is performed. In this step, due to the shape of the remaining silicon oxide film, 111
And 112 form low-concentration impurity regions. The length of this low-concentration impurity region is the distance indicated by y in (D).

That is, when P ions are implanted under the condition that the regions 110 and 113 become the source and drain regions,
Due to the presence of the silicon oxide film 104 ′, 110 and 11
As compared with the region of 3, the regions of 111 and 112 are implanted with impurities at a lower concentration.

Here, the low concentration impurity region 112 formed on the drain region 113 side becomes an LDD (lightly doped drain) region.

After the implantation of P ions is completed, laser light is irradiated to activate the implanted impurities and anneal the region damaged by the implantation of ions.

Thus, the source region 110, the low concentration impurity regions 111 and 112 (LDD regions), and the drain region 1 are formed.
13 is formed. (FIG. 3 (E))

Next, an interlayer insulating film 114 is formed, and then a source electrode 115 and a drain electrode 116 are formed. Thus, a thin film transistor having an LDD region formed in a self-aligned manner is obtained. (FIG. 3 (F))

The steps described above are characterized in that the LDD region 112 having a distance indicated by y can be formed in a self-aligned manner with the growth distance of the porous anodic oxide 107.

[0023]

When a thin film transistor obtained by the manufacturing process shown in FIG. 3 is manufactured, the following problems actually occur. FIG. 4 shows the state of the actual manufacturing process.

First, as shown in FIG. 4A, a base film (not shown) is formed on a glass substrate, and then an active layer 202 made of a crystalline silicon film is formed. Then, a silicon oxide film 203 which functions as a gate insulating film is formed.

Further, an aluminum film 204 is formed, and an extremely thin anodic oxide film 205 having a dense film quality is formed on the surface thereof. (Fig. 4 (A))

Next, the resist mask 200 is arranged, and the aluminum film 204 is patterned by the wet etching method.

At this time, due to the characteristic of wet etching in which substantially isotropic etching proceeds, etching is performed in the horizontal direction at a distance indicated by 208 (this distance is almost the same as the thickness of the aluminum film 204). proceed.
(FIG. 4 (B))

Further, since the aluminum oxide is hardly etched by the etchant for etching aluminum, the anodic oxide film having a dense film quality as indicated by 207 remains like an eaves.

Next, anodic oxidation is performed under the conditions for forming a porous anodic oxide film, whereby the porous anodic oxide 210 is formed.
Is formed. (FIG. 4 (C))

Next, the resist mask 200 is removed, and an anodized film is formed under the anodizing condition having a dense film quality. In this step, an anodic oxide film indicated by 212 is formed. (FIG. 4 (D))

This anodic oxidation is a porous anodic oxide 2
Since the electrolytic solution penetrates into 10, the anodic oxide film 212 is formed on the peripheral surface of the aluminum pattern (to be the gate electrode) indicated by 211.

The anodic oxide film 2 having this dense film quality
12 is integrated with the anodic oxide film 207 having an extremely thin and dense film quality.

Thus, the state shown in FIG. 4D is obtained. Next, the silicon oxide film 203 is etched. At this time, 20
The anodic oxide film having a dense film quality shown by 7 remains in an eaves shape. Therefore, the silicon oxide film 213 remains in a range larger than expected.

Then, a low concentration impurity region (LDD region) is formed with a size different from the design value.

Since the anodic oxide film remaining in the shape of an eaves is thin, its existence is not certain. Therefore, the above state becomes a factor that makes the manufacturing process unstable and lowers the manufacturing yield.

In particular, the variation in the size of the low concentration impurity region has a great influence on the operation of the thin film transistor.

An object of the invention disclosed in this specification is to provide a technique capable of obtaining an LDD region with high reproducibility.

[0038]

One of the inventions disclosed in this specification is, as shown in the manufacturing process of FIG. 1, a film 304 (FIG. 1) made of a material capable of anodizing on a gate insulating film 303. In the case of, the step of forming an aluminum film (FIG. 1
(A)), a step of forming an anodized film 305 on the film, and a mask 30 on the film made of the anodizable material.
6 is arranged and the anodizable material is patterned using an isotropic etching method (FIG. 1B).
And a step of performing the patterning (see FIG. 1).
In (B)), the anodic oxide film 307 is a film pattern 306 made of a patterned anodizable material.
A step of removing the anodic oxide film that protrudes and remains under the mask 300 and remains under the mask (FIG. 1).
(C)).

According to another structure of the invention, as shown in the manufacturing process of FIG. 1, a step of forming a film 304 made of an anodizable material on the gate insulating film 303 (FIG. 1A), A step of forming an anodic oxide film (FIG. 1A) on the film, a mask 300 is placed on the film made of the anodizable material, and the anodization can be performed using an isotropic etching method. The step of patterning a material (FIG. 1B) and the step of removing the mask (FIG. 1E) are performed, and in the step of performing the patterning, the anodic oxide film 30 is formed.
7 is a step of protruding from the film pattern 306 made of an anodizable material and remaining under the mask 300, and removing the anodic oxide film remaining under the mask before removing the mask (FIG. 1 ( C)).

In the structure of another invention, as shown in the manufacturing process of FIG. 1, a step of forming a film 304 made of an anodizable material on the gate insulating film 303 (FIG. 1A), A step of forming an anodized film 305 having a dense film quality on the film 304 (FIG. 1A), a mask 306 is placed on the film 305 made of the anodizable material, and isotropic etching is performed. Patterning the anodizable material using a method (FIG. 1 (B)), and removing the anodic oxide film 307 having a dense film quality that exists outside the porous anodic oxide. A step (FIG. 1C) and a step (FIG. 1D) of selectively forming a porous anodic oxide 310 on the side surface of the pattern obtained in the patterning step. Characterize.

In the structure of another invention, as shown in a specific manufacturing process in FIG. 1, a step of forming a gate insulating film 303 to cover the active layer 302 (FIG. 1A) and a gate insulating film. A step of forming a film 304 made of an anodizable material on the film 303 (FIG. 1A) and a step of forming an anodized film 305 having a dense film quality on the film 304 (FIG. 1).
(A)) and a step of disposing a mask 300 on the film 304 made of the anodizable material and patterning the anodizable material using an isotropic etching method (FIG. 1B). And an anodic oxide film 307 having a dense film quality that exists outside the porous anodic oxide.
(FIG. 1C) and a step of selectively forming a porous anodic oxide 310 on the side surface of the pattern obtained by the patterning (FIG. 1D).
And a step of removing the mask (FIG. 1E) and a step of removing the exposed gate insulating film (FIG. 1F).
And a step of removing the porous anodic oxide film 310 (FIG. 2A) and a step of implanting impurity ions into the active layer (FIG. 2A). And

In the above structure, by implanting impurity ions (step of FIG. 2A), a channel formation region 316 is formed in the active layer below the pattern 311 made of the remaining anodizable material. Low-concentration impurity regions (LDD regions) 315 and 31 in which an impurity is added to the active layer below the portion 310 where the porous anodic oxide was present in a concentration lower than that of the source and drain regions.
7 is formed.

[0043]

【Example】

[Embodiment 1] FIGS. 1 and 2 show a manufacturing process of a thin film transistor of this embodiment. First, a base film (not shown) is formed on the glass substrate 301. Here, as the base film, 3000
Å A thick silicon oxide film is formed. As a film forming method, a sputtering method is used. A quartz substrate may be used as the substrate.

Next, the amorphous silicon film (not shown) is subjected to decompression heat CV.
A film is formed to a thickness of 500Å by the D method. By further irradiating with laser light, this amorphous silicon film is crystallized and transformed into a crystalline silicon film. The laser light uses a KrF excimer laser (wavelength 248 nm).

After the crystalline silicon film is obtained, patterning is performed to form an island-shaped pattern 302 which will be the active layer of the thin film transistor. (Fig. 1 (A))

Next, the silicon oxide film 3 used when forming the gate insulating film and the low concentration impurity region (LDD region).
03 is formed. As a film forming method, a plasma CVD method is used. The thickness of the silicon oxide film 303 is 3000 Å.

Further, an aluminum film 304 which will later become a gate electrode is formed on the silicon oxide film 303. A sputtering method is used as a film forming method. The thickness is 40
00 °.

0.18% by weight of scandium is contained in this aluminum film. This is to prevent hillocks and whiskers from being formed in a subsequent step (particularly, a step in which heating is performed).

Hillocks and whiskers are needle-like or stab-like protrusions formed by abnormal growth of aluminum.

After forming the aluminum film 304, the anodic oxide film 305 having a thickness of 100 Å is formed under the condition of forming a dense anodic oxide film. (Fig. 1 (A))

The anodic oxidation here is 3% as an electrolytic solution.
The solution obtained by neutralizing the retylene glycol solution containing tartaric acid in Example 1 with ammonia water is used. In the anodic oxidation, the aluminum film 304 is used as an anode in the electrolytic solution.
Platinum is used as a cathode and an electric current is passed between both electrodes. The film thickness can be controlled by the applied voltage.

The anodic oxide film 305 formed here has a dense film quality. The anodic oxide film 305 is required to improve the adhesiveness of the resist mask to be subsequently placed on the aluminum film 304. Further, it has a function of masking the upper surface of the aluminum pattern so that the growth proceeds only on the side surface of the gate electrode when the porous anodic oxide is formed later.

Thus, the state shown in FIG. 1A is obtained. Next, the resist mask 300 is arranged. Then, a pattern indicated by 306 is formed by the wet etching method.

Here, as an etchant, first, the anodic oxide film 305 is etched using chromium mixed acid, and then aluminum is etched using aluminum mixed acid.

The chromium mixed acid is a mixture of aluminum mixed acid described later in which chromium oxide is purely dissolved.

The aluminum mixed acid is a solution in which nitric acid, acetic acid, phosphoric acid, and water are mixed, and has the ability to selectively etch aluminum.

The etching here is isotropic etching. As a method other than the wet etching, isotropic dry etching can be used.

When the above etching using aluminum mixed acid is performed, the aluminum film is also etched in the horizontal direction. The traveling distance 308 of the etching in the horizontal direction is
The film thickness of the aluminum film 304 is about 309.

In this embodiment, the aluminum film 30 is used.
Since the film thickness of 4 (indicated by 309) is 4000Å, the distance indicated by 308 is also approximately 4000Å.

At this time, the anodic oxide film 3 having a dense film quality
05 remains in the shape as shown at 307. Thus, the state shown in FIG. 1B is obtained.

After obtaining the state shown in FIG. 1B, the anodic oxide film 307 having a dense film quality and protruding from the aluminum pattern 306 is removed. Here, wet etching using chromium mixed acid as an etchant is performed.

In this step, the canopy-like portion of the anodic oxide film 307 that protrudes from the aluminum pattern 306 is removed. Then, as indicated by 301, an extremely thin anodic oxide film remains. (Fig. 1 (C))

Chromium mixed acid is a mixture of chromic acid (CrO) in pure water.
_It is a mixture of ₃ ) and aluminum mixed acid.
This etchant has the ability to selectively etch aluminum oxide. In addition, since a passivation film is formed on the surface of aluminum, etching hardly progresses.

Next, a porous anodic oxide 310 is formed. This step is performed using a 3% oxalic acid aqueous solution as an electrolytic solution. The growth distance of the anodic oxide 310 can be controlled by the anodic oxidation time. (Fig. 1 (D))

Here, the growth distance of the anodic oxide 310 is 5000 Å. With this growth distance, a low-concentration impurity region can be formed later. The region indicated by 311 becomes the gate electrode.

In this step, the resist mask 30
0 exists, and the anodic oxide film 3 has a dense film quality.
Since 01 exists, the anodic oxidation selectively progresses on the side surface of the aluminum pattern to be the gate electrode 311.

After forming the anodic oxide 301, the resist mask 300 is then removed with a dedicated stripping solution. (Figure 1
(E))

Then, anodic oxidation is performed again. here,
Anodization is performed under the condition that an anodic oxide film having a dense film quality is formed.

This anodic oxidation condition is the same as that for forming the anodic oxide film 305. The conditions that determine the film thickness must be changed.

Here, an anodized film having a dense film quality indicated by 312 is formed with a thickness of 1200 Å. The anodic oxide film 312 has a very thin remaining thickness (here, a thickness of 10).
0Å) It is integrated with the anodic oxide film 301. (Figure 1
(E))

Thus, the state shown in FIG. 1 (E) is obtained. Next, the exposed portion of the silicon oxide film 303 is removed by etching.
Here, the exposed silicon oxide film 303 is etched by an etching method using the RIE method.

As a result of this step, the silicon oxide film 313 remains. (FIG. 1 (F))

After obtaining the state shown in FIG. 1F, impurity ions are implanted. Here, P (phosphorus) ions are implanted in order to manufacture an N-channel thin film transistor. If a P-channel type is to be manufactured, B (boron) is used.
Ion implantation is performed.

In this step, the remaining silicon oxide film 313 shields some of the implanted ions from the regions 315 and 317. Therefore, 315 and 3
Region 17 is a region in which impurity ions are implanted at a lower concentration than regions 314 and 318.

After implanting the impurity ions, laser light irradiation is performed to activate the implanted impurity ions and anneal damage to the regions into which the ions are implanted. A KrF excimer laser is used as the laser light.

Thus, as shown in FIG. 2A, the source region 314, the drain region 318, the channel forming region 316, and the low concentration impurity regions 315 and 317 are formed in a self-aligned manner.

Here, the low concentration impurity region indicated by 317 becomes the LDD region.

After obtaining the state shown in FIG. 2A, a silicon oxide film 319 is formed as an interlayer insulating film to a thickness of 5000 Å. A plasma CVD method is used as a film forming method.

Further, contact holes 320 and 321 are formed. Thus, the state shown in FIG. 2B is obtained.

Next, the source electrode 322 and the drain electrode 323 are formed with a laminated film of a titanium film, an aluminum film and a titanium film.

Finally, in a hydrogen atmosphere at 350 ° C., 1
The thin film transistor illustrated in FIG. 2B is completed by performing heat treatment for time.

[Embodiment 2] This embodiment shows a manufacturing process of a thin film transistor in which only an offset gate region is arranged without forming a low concentration impurity region corresponding to an LDD region.

FIG. 5 shows the manufacturing process of this embodiment. First,
A base film (not shown) is formed on a glass substrate 501, and an active layer 502 made of a crystalline silicon film is further formed. Further, a silicon oxide film 503 which functions as a gate insulating film is formed.

Then, an aluminum film 504 forming a gate electrode is formed. Further, an anodic oxide film 505 having a dense film quality is formed on the surface thereof. Anodized film 505
The film thickness is 100Å. Thus, the state shown in FIG.

Next, the resist mask 500 is arranged and patterned by the dry etching method shown in the embodiment 1 to a pattern 506. At this time, the anodic oxide film 507 having a dense film quality is also patterned at the same time. However, the patterns 506 and 507 are different as shown because of their resistance to etching. Thus, the state shown in FIG. 5B is obtained.

Next, the portion of the anodic oxide film 507 that overhangs in a canopy shape is removed using chromium mixed acid. FIG.
The state shown in (C) is obtained.

Next, the resist mask 500 is removed, and anodic oxidation is performed again. Also here, anodic oxidation is performed under the condition of forming an anodic oxide film having a dense film quality. Here, 50
An anodic oxide film shown by 7 is formed to a thickness of 1000Å. An offset gate region is formed later in the active layer with the thickness of the anodic oxide film 507. (FIG. 5 (D))

Next, the exposed portion of the silicon oxide film 503.
Are removed by a dry etching method. FIG.
The state shown in (D) is obtained. In this state, the silicon oxide film 508 remains.

When the state shown in FIG. 5D is obtained, the source /
Impurity ions are implanted to form a drain region. Here, implantation of B (boron) ions is performed by a plasma doping method in order to form a P-channel type.

In this step, as shown in FIG. 5D, the region 509 becomes the source region and the region 513 becomes the drain region. The region 711 becomes the channel formation region. Further, offset gate regions 510 and 512 are formed depending on the thickness of the anodic oxide film 507.

After the implantation of the impurity ions is completed, laser light irradiation is performed to activate the implanted impurity ions and anneal damage to the active layer generated at the time of implanting the ions.

Next, a silicon oxide film 514 is formed as an interlayer insulating film. Then, contact holes are formed, and a source electrode 515 and a drain electrode 516 are formed. Here, the source electrode and the drain electrode are formed of a laminated film of a titanium film, an aluminum film, and a titanium film.

[Third Embodiment] The thin film transistors described in the first and second embodiments can be used for an active matrix type liquid crystal display device and an active matrix type EL display device in which a peripheral drive circuit is integrated. These display devices are collectively referred to as flat panel displays.

These display devices can be used for the following applications. FIG. 6A shows a device called a digital still camera or an electronic camera.

This device has a function of electronically storing an image taken by a CCD camera arranged in the camera section 2002. A function of displaying the captured image on a display device 2003 arranged in the main body 2001 is provided. Further, there are also known ones that have various communication functions and information storage means and can be utilized as an information terminal. The operation of the device is performed by operation buttons 2004.

FIG. 6B shows a portable personal computer. This device is provided with a display device 2 on a cover (cover) 2102 which is attached to the main body 2101 and can be opened and closed.
104 is provided, and various information can be input and various operations can be performed from the keyboard 2103.

FIG. 6C shows an example in which a flat panel display is used in the car navigation system. The car navigation system includes a main body including an antenna unit 2304 and a display device 2302.

Switching of various information required for navigation is performed by the operation button 2303. Further, it is generally performed by a remote control device (not shown).

FIG. 6D shows an example of a projection type liquid crystal display device. In the figure, light emitted from a light source 2402 is optically modulated by a liquid crystal display device 2403 to form an image. The image layer is reflected by the mirrors 2404 and 2405 and displayed on the screen 2406.

[0100]

By utilizing the invention disclosed in this specification, the porous anodic oxide film 310 shown in FIG. 1 (C) is used.
The size of the low-concentration impurity region can be determined by the growth distance of.

That is, as shown in FIG. 1 (C), a portion of the anodic oxide film 307 having a dense film quality, which unintentionally remains, is protruded to remove a portion of the anodic oxide film. The size of the low concentration impurity region can be determined only by the growth distance of 310.

The LDD region can be obtained with high reproducibility. Then, the thin film transistor can be manufactured with a high production yield.

[Brief description of drawings]

1A to 1D are diagrams showing steps of manufacturing a thin film transistor using the invention disclosed in this specification.

2A to 2D are diagrams showing steps of manufacturing a thin film transistor using the invention disclosed in this specification.

FIG. 3 is a diagram showing a manufacturing process of a thin film transistor according to a conventional technique.

FIG. 4 is a diagram showing a manufacturing process of a thin film transistor according to a conventional technique.

5A to 5D are diagrams showing steps of manufacturing a thin film transistor using the invention disclosed in this specification.

6A to 6C are diagrams illustrating examples of various devices using an active matrix display device.

[Explanation of symbols]

301 glass substrate 302 active layer (crystalline silicon film) 303 gate insulating film (silicon oxide film) 304 aluminum film 305 anodized film having a dense film quality 300 resist mask 306 patterned aluminum film 307 having a remaining dense film quality Anodic oxide film 301 Remaining dense anodic oxide film 310 Porous anodic oxide film 311 Gate electrode 312 Anodized film 315 with dense film residual gate insulating film 314 Source region 315 Low concentration impurity region 316 Channel formation region 317 Low concentration impurity region (LDD region) 318 Drain region 319 Interlayer insulating film 320, 321 Contact hole 322 Source electrode 323 Drain electrode

Claims (6)

[Claims] 1. A step of forming a film made of an anodizable material on a gate insulating film, a step of forming an anodized film on the film, and a mask on the film made of the anodizable material. Place
A step of patterning the anodizable material using an isotropic etching method, wherein in the step of performing the patterning, the anodized film is a patterned film of the anodizable material. A method of manufacturing a semiconductor device, comprising: a step of removing an anodic oxide film that protrudes and remains under the mask and remains under the mask. 2. A step of forming a film made of an anodizable material on a gate insulating film, a step of forming an anodized film on the film, and a mask on the film made of the anodizable material. Place
The method comprises: patterning the anodizable material using an isotropic etching method; and removing the mask. In the patterning step, the anodized film is patterned anodizable. Fabrication of a semiconductor device characterized by including a step of protruding from a pattern of a film made of a different material and remaining under the mask, and removing the anodic oxide film remaining under the mask before removing the mask. Method. 3. A step of forming a film made of an anodizable material on a gate insulating film, a step of forming an anodized film having a dense film quality on the film, and a step of using the anodizable material. Place a mask on the film
Patterning the anodizable material using an isotropic etching method, and removing the anodic oxide film having a dense film quality that exists outside the porous anodic oxide, And a step of selectively forming a porous anodic oxide on a side surface of the pattern obtained in the patterning step, the method for manufacturing a semiconductor device. 4. The method for manufacturing a semiconductor device according to claim 1, wherein the anodizable material is aluminum. 5. A step of forming a gate insulating film so as to cover the active layer, a step of forming a film made of an anodizable material on the gate insulating film, and an anode having a dense film quality on the film. A step of forming an oxide film, arranging a mask on the film made of the anodizable material,
Patterning the anodizable material using an isotropic etching method, and removing the anodic oxide film having a dense film quality that exists outside the porous anodic oxide, A step of selectively forming a porous anodic oxide on a side surface of the pattern obtained by the patterning, a step of removing the mask, a step of removing an exposed gate insulating film, A method for manufacturing a semiconductor device, comprising: a step of removing a anodic oxide film having a shape; and a step of implanting impurity ions into the active layer. 6. The method according to claim 5, wherein by implanting impurity ions, a channel forming region is formed in the active layer under the pattern made of the remaining anodizable material, and the porous anodic oxide is formed. A method of manufacturing a semiconductor device, characterized in that a low-concentration impurity region in which an impurity is added at a lower concentration than that of a source and drain region is formed in an active layer below an existing portion.