JP3525773B2 - Nitride semiconductor substrate and nitride semiconductor device using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to an LED (light emitting diode), an SLD (super luminescent diode),
Nitride semiconductors (In _X Al _Y Ga _1-XY N, 0 ≦ X, which are used in light-emitting elements such as LDs (laser diodes), solar cells, light-receiving elements such as photosensors, or electronic devices such as transistors and power devices. , 0 ≦ Y, X + Y ≦
1) Regarding the device.

[0002]

2. Description of the Related Art Nitride semiconductors have recently been put to practical use as materials for high-intensity blue LEDs and pure green LEDs in full-color LED displays, traffic signals and the like. LEDs used for these various devices have a single-quantum-well (SQW) structure or a multi-quantum-well structure (MQW) between an n-type nitride semiconductor layer and a p-type nitride semiconductor layer. : Multi-Quantum-Well) InGa
It has a double hetero structure in which an active layer made of N is sandwiched. Wavelengths such as blue and green are determined by increasing or decreasing the In composition ratio of the InGaN active layer. The applicant has also used this material to produce 410n at room temperature under pulsed current.
world's first laser oscillation was announced (for example, Jpn.
J.Appl.Phys.35 (1996) L74, Jpn.J.Appl.Phys.35 (1996) L
217). This laser device has a double hetero structure having an active layer of a multiple quantum well structure using InGaN, and has a threshold current of 610 mA and a threshold current density of 8.7 kA / cm ^{2 under} the conditions of a pulse width of 2 μs and a pulse period of 2 ms. Four
Oscillation of 10 nm is shown. The applicant also succeeded in continuous oscillation at room temperature for the first time, and announced (for example, Nikkei Electronics December 2, 1996 Technical Bulletin, Appl.Phys.Let).
t.69 (1996) 3034-, Appl.Phys.Lett.69 (1996) 4056-
etc). This laser device exhibits continuous oscillation for 27 hours at 20 ° C., with a threshold current density of 3.6 kA / cm ² , a threshold voltage of 5.5 V, and an output of 1.5 mW.

Sapphire is used as a growth substrate of a nitride semiconductor in both the LED element and the laser element. As is well known, sapphire has a lattice mismatch of 1 with a nitride semiconductor.
Since the amount is 3% or more, the crystal of the nitride semiconductor grown on this has many crystal defects. In addition to sapphire, devices using substrates such as ZnO, GaAs, and Si have been reported, but these substrates also do not lattice match with the nitride semiconductor and have better crystallinity than sapphire. Have not been realized even for LEDs, because of the difficulty of growing.

As a technique for growing a nitride semiconductor having good crystallinity, for example, a technique for growing a nitride semiconductor on an off-angled sapphire substrate has been disclosed (for example, JP-A-4-299876 and 4-32388).
0, JP-A-5-55631, and JP-A-5-190903.
etc). These techniques are intended to obtain a nitride semiconductor with good crystallinity by making the inter-atomic distance between GaN and sapphire close by using a substrate that is continuously off-angled as a growth surface. However, it has not yet been put to practical use.

[0005]

In order to improve various characteristics such as output and life of a nitride semiconductor device, use of a GaN substrate lattice-matched with the nitride semiconductor causes less crystal defects and improves crystallinity. It is predicted that a good nitride semiconductor can be grown, but since there is no GaN substrate industrially, it is possible to improve output, life, etc. by using a substrate made of a material different from the nitride semiconductor such as sapphire, ZnO, and spinel. Is being pursued. Among them, sapphire has been put to practical use because it can grow a nitride semiconductor having the best crystallinity, but it is not yet satisfactory. Further, when growing a nitride semiconductor on a substrate, the surface of the obtained nitride semiconductor substrate was smooth by using a heterogeneous substrate which was off-angled on the step, but as a substrate for growing the nitride semiconductor, This was also unsatisfactory. The present invention has been made in view of such circumstances, and an object thereof is to provide a nitride semiconductor device with a long life, high efficiency, and high output by improving a substrate on which a nitride semiconductor is grown. It is to improve the yield.

[0006]

When growing a nitride semiconductor on a substrate, we are stepwise off-angled, and when the off-angle of the off-angle is 0.10 ° or more and 0.20 ° or less. Using a substrate made of a material different from that of a certain nitride semiconductor, a stripe-shaped protective film is further formed on the substrate, and a nitride semiconductor epitaxially grown by selective growth is grown on the protective film. Smoothes the nitride semiconductor device for a long life,
It was possible to obtain high output. That is, the nitride semiconductor substrate of the present invention has the first nitride semiconductor on the substrate whose main surface is the C-plane having an off angle of 0.10 ° or more and 0.20 ° or less, A stripe-shaped protective film different from the nitride semiconductor is provided on the first nitride semiconductor, and a second nitride semiconductor selectively grown on the first nitride semiconductor and the protective film is provided. The direction (step direction) along the step of the off-angled substrate is perpendicular to the plane A of the substrate, and the stripe-shaped protective film is
It is characterized in that it is parallel to a direction (step direction) along the step of the off-angled substrate. Further, the film thickness of the first nitride semiconductor is 1.5 μm or more and 6 μm or more.
m or less, the film thickness of the second nitride semiconductor is 5 μm or more,
The feature is that the thickness is 20 μm or less. In addition, the nitride semiconductor substrate of the present invention is off-angled in steps, and the first nitride film having a film thickness of 1.5 μm or more and 6 μm or less is formed on the substrate made of a material different from the nitride semiconductor. A nitride semiconductor, and a stripe-shaped protective film different from the nitride semiconductor on the first nitride semiconductor,
The second nitride semiconductor having a film thickness of 5 μm or more and 20 μm or less is provided on the first nitride semiconductor and the protective film, and the direction (step direction) along the step of the off-angled substrate is The stripe-shaped protective film is perpendicular to the plane A of the substrate and is parallel to a direction (step direction) along the step of the off-angled substrate. Further, the stripe of the protective film is characterized in that the width of the exposed portion of the protective film is 10 μm or less. Further, WS / WW, which is the ratio of the width (WW) of the exposed portion of the protective film and the width (WS) of the protective film, is larger than 1 and 2
It is characterized in that it is set to 0 or less. The substrate made of a material different from the nitride semiconductor is sapphire, spinel, Si
It is a substrate made of a material selected from the group consisting of C (including 6H and 4H), GaAs, Si and ZnO. Further, the nitride semiconductor device of the present invention is characterized in that the device structure is laminated on the surface of the nitride semiconductor substrate.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. FIG. 1 is an enlarged schematic view showing a cross section of a substrate used for the nitride semiconductor device of the present invention. The nitride semiconductor device of the present invention is thus grown on a heterogeneous substrate which is stepwise off-angled. The main surface is the C surface used as a different substrate (that is, the orientation flat surface is A
The sapphire substrate (which is a surface) is not particularly limited as long as it is a material other than the nitride semiconductor, and other conventionally known materials such as sapphire (including A surface and R surface), spinel, SiC (6H, 4H is included.), GaAs, S
You may use i, ZnO, etc.

Conventionally, the irregularities on the surface of the off-angled heterogeneous substrate tend to be inherited each time a layer is deposited and further increase or worsen. As described above, only by providing a conventional off-angled heterogeneous substrate or a buffer layer on the substrate, it is not possible to obtain good characteristics such as threshold current and device life.

However, the nitride semiconductor substrate formed according to the present invention is such that the first nitride semiconductor is first formed on the off-angled heterogeneous substrate, and the nitride formed on the first nitride semiconductor in a stripe shape perpendicular to the A surface of the sapphire substrate. Protective film different from semiconductor,
A second nitride semiconductor selectively grown thereon is further formed, and a direction (step direction) along the step of the off-angled sapphire substrate is formed perpendicular to the A-plane of the sapphire substrate. The stripe-shaped protective film is formed parallel to the direction (step direction) along the step of the off-angled sapphire substrate, so that the epitaxial growth surface (second nitride semiconductor surface) is The morphology was wavy as shown in the schematic diagram of No. 3, there was almost no unevenness, the obtained element was smooth, the threshold current was low, and the life characteristics were good. At this time, the surface of the first nitride semiconductor, which is the base, had a striped morphology as shown in the schematic view of FIG.

In the present invention, the heterogeneous substrate is different from the selective growth,
When a nitride semiconductor is grown after partially forming a protective film on the buffer layer or the nitride semiconductor layer, it grows in the thickness direction to some extent and then grows in the lateral direction.
It is to be formed into a film. Here, as the protective film, specifically, silicon oxide (SiO _x ), silicon nitride (Si
_X N _Y ), oxides such as titanium oxide (TiO _X ), zirconium oxide (ZrO _X ), nitrides, multilayer films of these, and metals having a melting point of 1200 ° C. or higher can be used. A vapor phase film forming technique such as vapor deposition, sputtering or CVD is used for forming the protective film, and a photolithography technique can be used for partial (selective) forming. As the shape of the protective film, for example, dots, stripes, or a checkerboard shape can be formed, but stripes are preferable. In the stripe of the protective film, the width of the exposed portion (window portion) of the protective film is 10 μm or less, more preferably 5 μm or less, and most preferably 3 μm.
Adjust as follows. To obtain further fewer nitride semiconductor substrate having crystal defects, the ratio W _S / W _W of the window width (W _W) and the width of the protective film (W _S) is be greater than 1 to 20 Desirably, preferably 10 or less.

In the present invention, the step-shaped off-angled heterogeneous substrate has a substantially horizontal terrace portion A and a step portion B as shown in FIG. The terrace portion A has few surface irregularities and is formed almost regularly. It is desirable that the stepped portion having such an off angle θ is formed continuously over the entire substrate,
In particular, it may be partially formed. Note that the off-angle θ indicates an angle between a straight line connecting the bottoms of a plurality of steps and the horizontal plane of the uppermost step, as shown in FIG. 1.

The off angle of the nitride semiconductor substrate of the present invention is 0.10 ° or more and 0.20 ° or less. By setting the off angle to be 0.10 ° or more and 0.20 ° or less,
The first nitride semiconductor surface has a striped morphology (see the schematic diagram of FIG. 2) and the epitaxial growth surface (second nitride semiconductor surface) has a wavy (see the schematic diagram of FIG. 3) morphology. The obtained nitride semiconductor device is smooth, and the characteristics thereof are long life, high efficiency, high output, and improved yield.

Here, when the off angle is smaller than 0.10 °, the first angle is set between 0.07 ° and 0.10 °.
The surface of the nitride semiconductor is scale-like (see the schematic diagram of FIG. 6), and the epitaxial growth surface is polygonal (see the schematic diagram of FIG. 5)
In the case of less than 0.07 °, the first nitride semiconductor surface has a cell-like morphology (see the schematic diagram of FIG. 4) and the epitaxial growth surface has a polygonal morphology (see the schematic diagram of FIG. 5). Therefore, the characteristics such as the lifetime are worse than those of the element obtained by the present invention.

When the off-angle is larger than 0.20 °, the surface of the first nitride semiconductor becomes a net having vertical cracks from the streaks, and the surface of epitaxial growth is wavy (see the schematic diagram of FIG. 3). As a result, the morphology in which the height difference of the waves is further increased, undulations are further observed, and the device characteristics deteriorate. FIG. 7 schematically shows the mesh morphology, and such a mesh is seen throughout.

[0015]

[Embodiment 1] Embodiment 1 will be described below. FIG. 8 is a schematic cross-sectional view showing the structure of a laser device using a nitride semiconductor layer obtained by the growth method of the present invention as a substrate. 2 inches φ, off-angle angle θ = 0.15 °, step difference (height) about 1 atomic layer, terrace width W has steps of about 40 Å, with C plane as the main plane and orientation flat plane as A plane As a step, a sapphire substrate having a direction along the step, that is, a step direction perpendicular to the plane A is prepared, and a nitride semiconductor layer is grown by the MOVPE method. First, a sapphire substrate was set in a reaction vessel, a layer of undoped GaN at 500 ° C. was set to 200 angstroms as a base layer, and subsequently set to a MOVPE apparatus to set 2 layers of undoped GaN at 1050 ° C. 0.5 μm, total film thickness about 2.5
A first nitride semiconductor layer having a thickness of μm is formed.

Next, after growing the first nitride semiconductor layer, a stripe-shaped photomask is formed on the surface of the first nitride semiconductor layer, and the stripe width is 10 μm by a CVD apparatus.
m, a protective film made of SiO _{2 with} a window of 2 μm 0.5 μm
It is formed with a film thickness of. At this time, the stripe direction was perpendicular to the sapphire A surface, that is, parallel to the step direction. After forming the protective film, the wafer is transferred to a reaction container, and TMG and ammonia are used as source gases at 1050 ° C. to grow a second nitride semiconductor layer made of undoped GaN with a film thickness of 15 μm. A nitride semiconductor substrate is obtained as described above. The surface of the obtained nitride semiconductor substrate was smooth although some undulations were observed, and the surface morphology was streaky on the first nitride semiconductor (see the schematic diagram of FIG. 2) and on the second nitride semiconductor. It was wavy (see the schematic diagram of FIG. 3).

Next, a structure to be an element is formed on the obtained nitride semiconductor substrate. First, GaN or AlGa
N-side contact layer 4 made of N, crack prevention layer 5 made of InGaN (this can be omitted), AlG.
n-side cladding layer 6 made of a superlattice of aN and Si-doped GaN, n-side optical guide layer 7 made of GaN, InGa
Multiple quantum well structure (MQW) active layer 8 made of N, M
p-side cap layer 9 made of g-doped AlGaN, Mg
P-side optical guide layer 10 made of doped GaN, AlGa
A p-side clad layer 11 made of a superlattice of N and Mg-doped GaN and a p-side contact layer 12 made of Mg-doped GaN are sequentially stacked.

Next, part of the p-side contact layer is etched to expose the n-side contact layer. Further, the p-side layer is etched up to the p-side clad layer by RIE to form a ridge, and an insulating film 3 such as TiO ₂ is formed on the ridge as a protective film.
A p-electrode 20, a p-pad electrode 21, and an n-electrode 22 and an n-pad electrode 23 are formed on 1 and each contact layer.

The laser chip obtained as described above was placed face up (a state where the substrate and the heat sink were opposed to each other) on the heat sink, each electrode was wire-bonded, and continuous oscillation was attempted at room temperature.
At a threshold current density of ² kA / cm ² and an output of 20 mW, continuous oscillation with an oscillation wavelength of 405 nm was confirmed, and 100
It showed a life of 0 hours or more.

[Comparative Example 1] For comparison, a sapphire substrate having a C-plane as a main surface and an orientation flat surface as an A-plane, in which a step is provided in a direction parallel to the A-plane,
The nitride semiconductor is grown, and the stripe direction of the protective film to be formed is perpendicular to the sapphire A surface, that is, perpendicular to the step direction. Others were laminated in the same manner as in Example 1 to manufacture a laser device. The obtained laser device had a higher threshold current and poorer life characteristics than the device of Example 1.

[Comparative Example 2] For comparison, a sapphire substrate which is not off-angled is used as a different type substrate.
Others were laminated in the same manner as in Example 1 to manufacture a laser device.
Some of the obtained laser elements had unstable laser oscillation, higher threshold currents, and shorter life characteristics than the elements of Example 1, and the element characteristics varied. The morphology of the first nitride semiconductor surface was cellular (see the schematic diagram of FIG. 4), and the morphology of the second nitride semiconductor surface was polygonal (see the schematic diagram of FIG. 5).

[Comparative Example 3] For comparison, a sapphire substrate having an off-angle of 0.3 ° was used as a different type substrate, and other layers were laminated in the same manner as in Example 1 to fabricate a laser device. When a sapphire substrate with an off-angle of 0.3 ° is used, the first nitride semiconductor surface becomes a mesh with vertical cracks (see the schematic diagram of FIG. 7), and the epitaxial growth surface has a wavy shape. (See the schematic diagram of FIG. 3), the morphology in which the height difference of the wave is further increased, undulation is further observed, and the threshold current is higher than that of the element of Example 1.

Example 2 A nitride semiconductor substrate was obtained in the same manner as in Example 1 except that a sapphire substrate having an off-angle angle of θ = 0.20 ° was used as the heterogeneous substrate. The surface of the obtained nitride semiconductor substrate was smooth although some waviness was observed, and the surface morphology was similar to that in Example 1 on the first nitride semiconductor (see the schematic diagram of FIG. 2). It was wavy (see the schematic diagram of FIG. 3) on the nitride semiconductor of No. 2. Subsequently, in the same manner as in Example 1, when a laser element was produced by forming a structure to be an element on the nitride semiconductor substrate, almost the same characteristics as in Example 1 were obtained.

[Third Embodiment] In the first embodiment, the film thickness of the second nitride semiconductor layer made of undoped GaN is set to 20.
A nitride semiconductor substrate was obtained in the same manner except that the film was grown to a film thickness of μm. The surface of the obtained nitride semiconductor substrate is the same as in Example 1.
The surface was smooth like the above, and warpage was conspicuous as compared with Example 1. However, the surface morphology on the second nitride semiconductor was wavy (see the schematic diagram in FIG. 3), and the characteristics were slightly inferior, but the yield was poor.

[Fourth Embodiment] In the first embodiment, the same film formation is performed until the first nitride semiconductor and the protective film are formed on the sapphire substrate. Then, as a second nitride semiconductor,
Undoped GaN by MOVPE 15μm, then H
It is formed by VPE with a film thickness of 100 μm. The surface of the obtained wafer was smooth as in Example 1, although some undulations were observed, and the surface morphology was streaky on the first nitride semiconductor (see the schematic diagram of FIG. 2) and second nitriding. It was wavy (see the schematic diagram in FIG. 3) on the object semiconductor. Next, the sapphire substrate and the first nitride semiconductor layer of the obtained wafer are polished and removed to expose the second nitride semiconductor layer, and the nitride semiconductor substrate having only the nitride semiconductor layer with a thickness of about 80 μm. Got

Next, the nitride semiconductor substrate is set in a reaction vessel, the foreign substrate is removed, and the following layers are formed on the surface opposite to the exposed surface. First, the n-side contact layer 4 made of GaN or AlGaN, the crack prevention layer 5 made of InGaN (this can be omitted), and AlGaN.
N-side cladding layer 6 made of a superlattice of Si and GaN doped with Si, an n-side optical guide layer 7 made of GaN, an active layer 8 of a multiple quantum well structure (MQW) made of InGaN, and a p-side made of AlGaN doped with Mg. The cap layer 9, the p-side optical guide layer 10 made of Mg-doped GaN, the p-side cladding layer 11 made of a superlattice of AlGaN and Mg-doped GaN, and the p-side contact layer 1 made of Mg-doped GaN.
2 are laminated in order.

After the completion of the reaction, the p
The mold contact layer and the p-type cladding layer were etched to form a ridge shape having a stripe width of 4 μm.
At this time, the ridge is such that the resonator direction of the obtained device is substantially parallel to the step direction of the nitride semiconductor substrate.
A p electrode 20 and a p pad electrode 21 are formed on the entire surface of this ridge.
To form. After forming the p-electrode, the n-electrode 22 and the n-pad electrode 23 are formed on the entire surface of the nitride semiconductor layer where the element structure is not formed.

The laser chip shown in FIG. 9 obtained as described above is placed face up (the substrate and the heat sink face each other) on the heat sink, and each electrode is wire-bonded to perform continuous oscillation at room temperature. When tried, as in Example 1, the threshold current density was 2 kA / cm.
^{At 2} and 20 mW output, continuous oscillation with an oscillation wavelength of 405 nm was confirmed, and a life of 1000 hours or more was shown.

[Embodiment 5] In Embodiment 4, except that a sapphire substrate having an off-angle angle of θ = 0.20 ° is used as the heterogeneous substrate, nitriding is performed only with a nitride semiconductor in the same manner as in Embodiment 4. A semiconductor substrate was obtained. The surface of the obtained nitride semiconductor substrate was smooth with some waviness, and the surface morphology was wavy on the second nitride semiconductor as in Example 4. Subsequently, in the same manner as in Example 4, when a laser element was manufactured by forming a structure serving as an element on the nitride semiconductor substrate, almost the same characteristics as in Example 4 were obtained.

[0030]

As described above, according to the present invention, the first nitride semiconductor is formed on the sapphire substrate whose main surface is the C-plane having an off angle of 0.10 ° or more and 0.20 ° or less. A protective film different from the nitride semiconductor formed in a stripe shape thereon and a second nitride semiconductor formed on the protective film, and the direction (step direction) along the step of the off-angled sapphire substrate is The protective film, which is formed perpendicularly to the surface A of the sapphire substrate and is formed in the stripe shape, is formed parallel to the direction (step direction) along the step of the sapphire substrate. Further, the film thickness of the first nitride semiconductor is 1.5 μm or more, 6
The thickness of the second nitride semiconductor is 5 μm or more and 20 μm or less. By thus improving the substrate on which the nitride semiconductor is grown, the surface of the nitride semiconductor can be made smooth, and the nitride semiconductor device can have a long life and high output.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an enlarged part of a substrate used for a nitride semiconductor device of the present invention.

FIG. 2 is a schematic diagram when a morphology of a nitride semiconductor surface of an example of the present invention is observed with a microscope.

FIG. 3 is a schematic diagram when observing the morphology of the surface of a nitride semiconductor of an example of the present invention with a microscope.

FIG. 4 is a schematic view of a morphology of a nitride semiconductor surface of an example of the present invention observed with a microscope.

FIG. 5 is a schematic diagram when a morphology of a nitride semiconductor surface of an example of the present invention is observed with a microscope.

FIG. 6 is a schematic diagram when observing the morphology of the surface of a nitride semiconductor of an example of the present invention with a microscope.

FIG. 7 is a schematic diagram when observing the morphology of the surface of a nitride semiconductor of an example of the present invention with a microscope.

FIG. 8 is a schematic sectional view showing a nitride semiconductor laser device according to an example of the present invention.

FIG. 9 is a schematic sectional view showing a nitride semiconductor laser device according to an example of the present invention.

[Simple explanation of symbols]

1 ... Sapphire substrate 2 ... Nitride semiconductor substrate 3 ... First nitride semiconductor 4 ... Second nitride semiconductor 5 ... n-side contact layer 6 ... Crack prevention layer 7 ... n-side clad layer 8 ... n-side light guide layer 9 ... Active layer 10 ... p-side cap layer 11 ... p-side light guide layer 12 ... p-side clad layer 13 ... p-side contact layer 20 ... p electrode 21 ... p pad electrode 22 ... n electrode 23 ... n pad electrode 30 ... Protective film 31 ... Insulating film

Claims (7)

(57) [Claims] 1. A step-shaped off-angle ,
The off-angle of the off-angle is 0.10 ° or more, 0.20 °
A first nitride semiconductor is provided on a substrate made of a material different from the following nitride semiconductor, and a stripe-shaped protective film different from the nitride semiconductor is provided on the first nitride semiconductor. A second nitride semiconductor is provided on the first nitride semiconductor and the protective film, and a direction (step direction) along the step of the off-angled substrate is perpendicular to the A surface of the substrate. And the stripe-shaped protective film is in a direction (step direction) along the step of the off-angled substrate.
A nitride semiconductor substrate which is parallel to the. 2. The film thickness of the first nitride semiconductor is 1.5.
The nitride semiconductor substrate according to claim 1, wherein the second nitride semiconductor has a thickness of 5 μm or more and 6 μm or less and a film thickness of the second nitride semiconductor is 5 μm or more and 20 μm or less. 3. A step-shaped off-angle ,
On a substrate made of a material different from the nitride semiconductor , the film thickness is
A first nitride semiconductor having a thickness of 1.5 μm or more and 6 μm or less, a stripe-shaped protective film different from the nitride semiconductor on the first nitride semiconductor, and The film thickness is 5 μm or more, 20 μ or more on the nitride semiconductor and the protective film.
a second nitride semiconductor having a thickness of m or less, and a direction (step direction) along the step of the off-angled substrate is
A nitride semiconductor substrate, which is perpendicular to the surface A of the substrate and in which the stripe-shaped protective film is parallel to a direction (step direction) along a step of the off-angled substrate. . 4. The stripe of the protective film is the dew of the protective film.
The width of the protruding portion is set to 10 μm or less.
Item 5. A nitride semiconductor substrate according to item 1 or 3. 5. The width (WW) of the exposed portion of the protective film and the protection
WS / WW, which is the ratio of the protective film width (WS), is greater than 1.
It is 20 or less.
Semiconductor substrate. 6. A material different from that of the nitride semiconductor
Substrates are sapphire, spinel, SiC (6H, 4H
Including. ), GaAs, Si, ZnO
2. A substrate made of a selected material.
6. The nitride semiconductor substrate according to any one of 5 to 5. 7. A nitride semiconductor device, wherein an element structure is laminated on the surface of the nitride semiconductor substrate according to any one of claims 1 to 6.