JP2008147552A - Nitride semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a group III-V nitride semiconductor device having a high breakdown voltage and a low on-voltage. <P>SOLUTION: The device includes: first and second nitride semiconductor layers made of a nitride semiconductor laminated on a semi-insulating substrate or an insulating one; a third nitride semiconductor layer film-formed at temperature lower than that of the second nitride semiconductor layer; a first anode electrode that forms Schottky junction on the first nitride semiconductor layer exposed in a recess and has low Schottky barrier height; a second anode electrode that is connected to the first anode electrode and is made of metal that is the same as or different from that of the first anode electrode forming the Schottky junction in the third nitride semiconductor layer; and a cathode electrode forming ohmic junction in the first, second, or third nitride semiconductor layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a group III-V nitride semiconductor device, and more particularly to a nitride semiconductor device that has a high breakdown voltage and a low on-resistance and is suitable as a switching element for high power.

A switching element for high power made of a semiconductor device is required to have a high breakdown voltage and a low on-resistance. Therefore, a power MOSFET (Metal Oxide Semiconductor FET) or an IGBT (Insulated Gate Bipolar Transistor) in which a bipolar transistor and a MOSFET are combined is used as a switching element. On the other hand, SiC semiconductor devices and III-V nitride semiconductor devices are known as semiconductor devices with high breakdown voltage and low on-resistance. Among these, specific applications of electronic devices that take advantage of the physical properties of III-V nitride semiconductors are desired, and the development of Schottky barrier diodes has been reported (Non-Patent Document 1).
Yoshida et al., “Low On-Voltage Operation GaN-FESBD”, IEICE Technical Report, The Institute of Electrical Engineers of Japan, 2004, EDD-04-69, p17-21

  Group III-V nitride semiconductor devices, which are being developed as semiconductor devices with high breakdown voltage and low on-resistance, are in the process of development, and there are very few reported examples that fully take advantage of their physical properties. An object of the present invention is to provide a group III-V nitride semiconductor device having a high breakdown voltage and a low on-voltage.

  In order to achieve the above object, the invention according to claim 1 of the present application provides a group III element consisting of at least one of the group consisting of gallium, aluminum, boron and indium and a group consisting of nitrogen, phosphorus and arsenic on the substrate. A first group III-V nitride semiconductor layer composed of a group III-V nitride semiconductor layer composed of a group V element containing at least nitrogen, and on the first group III-V nitride semiconductor layer The III-V nitride semiconductor layer stacked on the second layer, and does not contain aluminum, and the III-V nitride semiconductor layer stacked on the second group III-V nitride semiconductor layer. A third group III-V nitride semiconductor layer composed of a group V-nitride semiconductor layer, which is a film having a lower deposition temperature than the first and second group III-V nitride semiconductor layers. In the nitride semiconductor device, the third and second III-V A first anode electrode that is partially concaved and has a Schottky junction with the first group III-V nitride semiconductor layer exposed in the recess, and is the same as or different from the first anode electrode A second anode electrode made of metal and having a Schottky junction with the third group III-V nitride semiconductor layer and electrically connected to the first anode electrode, the first anode electrode and the first anode electrode The height of the Schottky barrier of the junction formed between the third group III-V nitride semiconductor layer is formed between the second anode electrode and the third group III-V nitride semiconductor layer. It is characterized by being lower than the height of the Schottky barrier of the junction.

  The invention according to claim 2 of the present application includes, on the substrate, a group III element consisting of at least one of the group consisting of gallium, aluminum, boron and indium and at least nitrogen of the group consisting of nitrogen, phosphorus and arsenic. A first III-V nitride semiconductor layer composed of a III-V nitride semiconductor layer composed of a group V element, and the III-V stacked on the first III-V nitride semiconductor layer A second group III-V nitride semiconductor layer which is made of a group nitride semiconductor layer and does not contain aluminum, and the group III-V nitride semiconductor layer stacked on the second group III-V nitride semiconductor layer A nitride semiconductor device in which a third group III-V nitride semiconductor layer made of a film having a lower deposition temperature than the first and second group III-V nitride semiconductor layers is sequentially stacked; Schottky contact with the third group III-V nitride semiconductor layer And a first Schottky junction to the third group III-V nitride semiconductor layer other than a portion in contact with the first anode electrode and made of a metal different from the first anode electrode. A second anode electrode electrically connected to the anode electrode, and a height of a Schottky barrier of a junction formed between the first anode electrode and the third group III-V nitride semiconductor layer is The height of the Schottky barrier of the junction formed between the second anode electrode and the third group III-V nitride semiconductor layer is lower.

  The invention according to claim 3 of the present application is the nitride semiconductor device according to claim 1 or 2, wherein the third group III-V nitride semiconductor layer has a microcrystalline structure.

  The invention according to claim 4 of the present application is the nitride semiconductor device according to any one of claims 1 to 3, wherein the first III-V is provided between the substrate and the first group III-V nitride semiconductor layer. A fourth group III-V nitride semiconductor layer made of the group III-V nitride semiconductor having an energy gap smaller than that of the group V nitride semiconductor layer is provided.

  The invention according to claim 5 of the present application is the nitride semiconductor device according to any one of claims 1 to 4, wherein the second, third, and fourth group III-V nitride semiconductor layers are the first III- It has an energy gap smaller than that of the group V nitride semiconductor layer.

  In the nitride semiconductor device of the present invention, under the condition of a low forward bias, a current flows through a Schottky junction with a low Schottky barrier height, resulting in a low on-voltage characteristic. A current also flows through a Schottky junction with a high barrier, and a large current can flow. In addition, under the low reverse bias condition, the reverse leakage current is small, and under the high reverse bias condition, only a high Schottky barrier junction functions and high breakdown voltage characteristics are obtained. In particular, in the nitride semiconductor device of the present invention, since a Schottky junction is formed in the third III-V nitride semiconductor layer having a high insulating microcrystalline structure, reverse leakage under a low reverse bias condition is achieved. The current can be greatly reduced.

  In order to form junctions having different Schottky barrier heights, a part of the nitride semiconductor layer is removed or a recess is formed by selective growth to form the first III-V nitride semiconductor layer and the third An anode electrode bonded to each of the group III-V nitride semiconductor layers may be formed, and can be easily formed. In particular, in the nitride semiconductor device of the present invention, the height of the Schottky barrier formed in the third III-V nitride semiconductor layer having a high insulating microcrystalline structure is the normal film formation temperature (growth temperature). It becomes higher than the height of the Schottky barrier formed in the nitride semiconductor layer formed in (1). As a result, the difference in the height of the Schottky barrier becomes large, and higher breakdown voltage characteristics can be obtained.

In addition, since the second III-V nitride semiconductor layer is laminated immediately below the third III-V nitride semiconductor layer, the effects of spontaneous polarization and piezo polarization are further increased. The key barrier height increases.

  Furthermore, in order to form junctions having different Schottky barrier heights, the anode electrode joined to the third group III-V nitride semiconductor layer may be formed of a different metal, which can be easily formed.

  In the case where the Schottky barrier diode of the present invention is formed using a so-called HEMT structure nitride semiconductor layer including a fourth group III-V nitride semiconductor layer and a two-dimensional electron gas is used as a carrier. Further, good forward voltage characteristics with a low on-voltage and a large forward current were obtained.

  In the nitride semiconductor device of the present invention, the first and second group III-V nitride semiconductor layers and the third group III-V nitride semiconductor layer having a highly insulating microcrystalline structure are stacked on the substrate. Forming a first anode electrode and a second anode electrode that are joined to the first and third group III-V nitride semiconductor layers, respectively, or joined to the third group III-V nitride semiconductor layer. By appropriately selecting the electrode metal, the first and second anode electrodes have different Schottky barrier heights. Further, the cathode electrode is structured to be bonded to the first, second or third group III-V nitride semiconductor layer.

  In the nitride semiconductor device having such a structure, when a forward bias is applied between the first and second anode electrodes and the cathode electrode, the first III-V group is used at the initial stage where the forward bias is small. The first anode electrode that forms a junction having a low height between the nitride semiconductor layer and the Schottky barrier functions mainly, whereby a current flows with a low on-voltage. When the forward bias is further increased, a current flows through the second anode electrode, and a large current flows.

  When a reverse bias is applied between the first and second anode electrodes and the cathode electrode, the third III-V nitride semiconductor layer has a highly insulating microcrystalline structure under low reverse bias conditions. Therefore, the reverse leakage current is reduced. When the reverse bias is further increased, only the second anode electrode that forms a junction with a high Schottky barrier functions, and high breakdown voltage characteristics are obtained. Hereinafter, the nitride semiconductor device of the present invention will be described in detail by taking a Schottky barrier diode that can be used as a switching element as an example.

  1 and 2 show a field effect Schottky barrier diode 10a using a HEMT structure according to a first embodiment of the present invention. FIG. 1 shows a sectional view thereof and FIG. 2 shows a manufacturing process thereof. . As shown in FIG. 2, aluminum nitride (AlN) having a thickness of about 200 nm is formed on a substrate 11 made of semi-insulating or insulating silicon carbide (SiC) by MOCVD (Metal-Organic Chemical Vapor Deposition) method or the like. A buffer layer 12, a channel layer 13 (corresponding to a fourth group III-V nitride semiconductor layer) made of non-doped gallium nitride (GaN) with a thickness of 2.5 μm, and a non-doped aluminum gallium nitride (AlGaN) with a thickness of 25 nm Schottky layer 14 (corresponding to the first group III-V nitride semiconductor layer) made of, and cap layer 15 (second group III-V nitride semiconductor layer made of non-doped gallium nitride (GaN) having a thickness of 5 nm. The gallium nitride film is formed at a temperature lower by about 600 ° C. than the film formation temperature of the cap layer 15 and has a microcrystalline structure and a high insulating thickness of 5 nm. A semiconductor substrate having a structure in which low-temperature growth cap layers 16 (corresponding to a third group III-V nitride semiconductor layer) made of (GaN) are sequentially stacked is prepared (FIG. 2a). In such a semiconductor substrate, a two-dimensional electron gas (carrier) is generated in the vicinity of the heterojunction surface between the channel layer 13 made of gallium nitride and the Schottky layer 14 made of aluminum gallium nitride.

Next, a cathode electrode 17 made of a laminate of titanium (Ti) / aluminum (Al) or the like is formed on the low-temperature growth cap layer 16 and subjected to rapid heating at 850 ° C. for 30 seconds. An ohmic junction is formed. Here, the cathode electrode 17 may have a structure in which the low temperature growth cap layer 16 and the cap layer 15 are removed by etching to make ohmic contact with the Schottky layer 14, but the low temperature remains in the microcrystalline structure after film formation. By forming an ohmic electrode on the growth cap layer 16, the metal constituting the ohmic electrode penetrates into the crystal grain boundary, and an ohmic electrode having a low contact resistivity (10 ⁻⁶ Ω · cm ² ) can be obtained. It is possible and preferable.

  Next, a photoresist is patterned so that the region where the first anode electrode is to be formed is opened, and the exposed low temperature growth cap layer 16 and cap layer 15 are all etched by dry etching such as RIE using a chlorine-based gas. Then, a recess 18 exposing the Schottky layer 14 is formed (FIG. 2b).

  Thereafter, a first anode electrode 19 made of a titanium (Ti) / aluminum (Al) laminate or the like is patterned on the Schottky layer 14 in the recess 18 (FIG. 2c). Further, a second anode electrode 20 made of a platinum (Pt) / gold (Au) laminate or the like is electrically connected to the first anode electrode 19 on the first anode electrode 19 and the low-temperature growth cap layer 16. Patterning is performed to form a Schottky junction with the low temperature growth cap layer 16 (FIG. 2d).

  In the field effect Schottky barrier diode 10a having such a structure, a Schottky barrier having a height of about 0.3 eV is formed by the junction of Ti constituting the first anode electrode 19 and AlGaN constituting the Schottky layer 14. Is done. On the other hand, a Schottky barrier having a height of about 2.0 eV is formed by the junction of Pt constituting the second anode electrode and the low temperature growth GaN constituting the low temperature growth cap layer 16. The height of the Schottky barrier is about 1.2 eV higher than the Schottky barrier height of the Schottky junction formed by the junction of GaN and Pt grown at a normal temperature.

  As described above, when a forward bias is applied between the first anode electrode 19 and the second anode electrode 20 and the cathode electrode 17 having different Schottky barrier heights, a forward voltage of 0.1 to 0.3 V is applied. A good rise was observed in which the directional current increased rapidly. When a reverse bias was applied, a large breakdown voltage of about 650 V was observed, and it was confirmed that the Schottky barrier diode had a high breakdown voltage and a low on-resistance.

  In general, in the Schottky barrier diode having such a structure, an on-voltage required for rising of a forward current at the junction of Ti and AlGaN is about 0.3 to 0.5V. On the other hand, the ON voltage of the junction between Pt and the low-temperature grown GaN of the present invention is about 2.0 to 2.5V.

  In the Schottky barrier diode 10a according to the present embodiment, the first anode electrode 19 (Ti) that is in Schottky junction with the Schottky layer 14 (AlGaN) mainly functions at the initial stage of rising of the forward current. It is considered that the ON voltage of the Schottky barrier diode 10 a is close to the ON resistance of the Schottky layer 14 and the first anode electrode 19. Furthermore, it is considered that the two-dimensional electron gas generated in the vicinity of the heterojunction surface between the channel layer 13 and the Schottky layer 14 serves as a carrier and contributes to an increase in forward current. Thereafter, when the forward bias reaches about 2.0 to 2.5 V, both the first anode electrode 19 and the second anode electrode 20 function as anode electrodes, and a larger current can be passed.

When a reverse bias was applied between the first anode electrode 19 and the second anode electrode 20 and the cathode electrode 17, a large breakdown voltage of about 650 V was observed. In general, when a reverse bias of −10 V is applied between the Ti electrode and the AlGaN layer that are Schottky-bonded to each other, a reverse leakage current of about 10 ⁻⁵ to 10 ⁻³ A is generated. On the other hand, the reverse leakage current when a Pt electrode and a low-temperature-grown GaN layer are subjected to Schottky junction is two orders of magnitude smaller than that, and a breakdown voltage of about 500 V is obtained.

  In the Schottky barrier diode 10a according to the present embodiment, in the first stage where the reverse bias is about −10 V or less, the reverse leak current hardly occurs due to the high insulation of the Schottky layer 14. When the reverse bias is larger than about −10 V, the two-dimensional electron gas serving as a carrier becomes almost non-existent due to the depletion layer formed by the junction between the second anode electrode 20 and the low-temperature growth cap layer 16, and slightly The reverse leakage current that is generated is prevented from flowing out. When the reverse bias is further increased, a depletion layer formed by the junction of the second anode electrode 20 and the low temperature growth cap layer 16 spreads, and only the second anode electrode 20 functions as an anode electrode, and the cap layer 15 By providing this, a high breakdown voltage of about 650 V is achieved.

  Next, a second embodiment in which the Schottky barrier diode having the structure shown in FIG. 1 is formed by another manufacturing method will be described. As in the first embodiment, a buffer layer 12 made of aluminum nitride (AlN) having a thickness of about 200 nm is formed on a substrate 11 made of semi-insulating or insulating silicon carbide (SiC) by MOCVD or the like. A channel layer 13 (corresponding to a fourth group III-V nitride semiconductor layer) made of non-doped gallium nitride (GaN) with a thickness of 0.5 μm, and a Schottky layer 14 (thickness of non-doped aluminum gallium nitride (AlGaN) with a thickness of 25 nm) A semiconductor substrate having a structure in which a group III-V nitride semiconductor layer 1) is sequentially stacked is prepared.

Next, a mask material made of SiO ₂ is formed in the region where the first anode electrode is to be formed on the Schottky layer 14 in order to selectively grow the cap layer, and thereafter, from non-doped gallium nitride (GaN) having a thickness of 5 nm. A cap layer 15 (corresponding to a second nitride semiconductor layer), which is formed at a temperature lower by about 600 ° C. than the film formation temperature of the cap layer 15, has a microcrystalline structure, and has a high insulation thickness of 5 nm. A low-temperature growth cap layer 16 (corresponding to a third nitride semiconductor layer) made of (GaN) is stacked. Thereafter, by removing the mask material, the recesses 18 described in the first embodiment can be formed. Hereinafter, according to the steps described in the first embodiment, the cathode electrode 17, the first anode electrode 19 and the second anode electrode 20 can be formed to form the Schottky barrier diode of the present invention.

  Thus, even when the non-doped GaN cap layer 15 and the low-temperature growth cap layer 16 are selectively grown without using etching, a nitride semiconductor having low on-voltage characteristics and high breakdown voltage characteristics as in the first embodiment described above. A device can be formed.

  FIG. 3 shows a Schottky barrier diode 10b according to a third embodiment of the present invention. As in the first embodiment, a buffer layer 12 made of aluminum nitride (AlN) having a thickness of about 200 nm is formed on a substrate 11 made of semi-insulating or insulating silicon carbide (SiC) by MOCVD or the like. A channel layer 13 (corresponding to a fourth group III-V nitride semiconductor layer) made of non-doped gallium nitride (GaN) with a thickness of 0.5 μm, and a Schottky layer 14 (thickness of non-doped aluminum gallium nitride (AlGaN) with a thickness of 25 nm) 1), a cap layer 15 (corresponding to a second group III-V nitride semiconductor layer) made of non-doped gallium nitride (GaN) having a thickness of 5 nm, The film is formed at a temperature lower by about 600 ° C. than the film formation temperature, has a microcrystalline structure, and has a low-temperature growth carrier made of gallium nitride (GaN) with a thickness of 5 nm, which is highly insulating. Flop layer 16 (corresponding to the third group III-V nitride semiconductor layer) is a semiconductor substrate stacked sequentially. Thereafter, a recess is formed, and an anode electrode made of titanium (Ti) / aluminum (Al) is formed so as to form a Schottky junction between the Schottky layer 14 and the low temperature growth cap layer 16. As shown in FIG. 3, the anode electrode of this example is formed by integrally forming a first anode electrode 19 that is bonded to the Schottky layer 14 and a second anode electrode 20 that is bonded to the low-temperature growth cap layer 16. ing. In such a structure, the height of the Schottky barrier between the first anode electrode 19 and the Schottky layer 14 and the second anode are compared with the case of being made of a different metal described in the first embodiment. The difference in the height of the Schottky barrier between the electrode 20 and the low temperature growth cap layer 16 is reduced. However, the Schottky barrier height of the Schottky junction bonded to the low-temperature growth cap layer 16 having the microcrystalline structure is higher than the Schottky barrier height of the Schottky junction bonded to the nitride semiconductor layer formed at the normal growth temperature. As a result, the low on-voltage characteristic and the high breakdown voltage characteristic are obtained. The recess 18 can also be formed by a selective growth method as described in the second embodiment.

  In this embodiment, the first anode electrode 19 and the second anode electrode 20 can be formed at the same time, and there is an advantage that the anode electrode forming process can be reduced.

  FIG. 4 shows a Schottky barrier diode 10c according to a fourth embodiment of the present invention. As in the first embodiment, a buffer layer 12 made of aluminum nitride (AlN) having a thickness of about 200 nm is formed on a substrate 11 made of semi-insulating or insulating silicon carbide (SiC) by MOCVD or the like. A channel layer 13 made of non-doped gallium nitride (GaN) having a thickness of .5 μm, a Schottky layer 14 made of non-doped aluminum gallium nitride (AlGaN) having a thickness of 25 nm (corresponding to the first nitride semiconductor layer), and undoped having a thickness of 5 nm. The cap layer 15 (corresponding to the second nitride semiconductor layer) made of gallium nitride (GaN) is formed at a temperature lower by about 600 ° C. than the film formation temperature of the cap layer 15, has a microcrystalline structure, and has an insulating property. A low-temperature growth cap layer 16 (corresponding to a third nitride semiconductor layer) made of gallium nitride (GaN) having a high thickness of 5 nm was sequentially stacked. To prepare the granulation of the semiconductor substrate. Thereafter, the first anode electrode 19 made of Ti and the second anode electrode 20 made of Pt are formed on the low-temperature growth cap layer 16 having a microcrystalline structure without forming a recess. In such a structure, the height of the Schottky barrier at the junction between the first anode electrode 19 and the low-temperature growth cap layer 16 is slightly higher than that in the first embodiment. By appropriately selecting electrode metals constituting the first and second anode electrodes 19 and 20 and forming junctions having different Schottky barrier heights, a relatively low on-voltage characteristic and a high level are obtained as in the first embodiment. A breakdown voltage characteristic is obtained.

  In the present embodiment, since it is not necessary to form the recess 18, there is an advantage that the process of forming the recess 18 can be reduced.

  As mentioned above, although the Example of this invention was described, it cannot be overemphasized that this invention is not limited to these. For example, instead of a nitride semiconductor device having a HEMT structure, a nitride semiconductor layer to which an impurity is added is used as an active layer (channel layer), and a low-temperature growth cap layer 16 having the above-described microcrystalline structure is formed thereon. A nitride semiconductor device having a so-called FET structure can be obtained. The nitride semiconductor layer is not limited to the GaN / AlGaN system, but a group III element consisting of at least one of the group consisting of gallium, aluminum, boron and indium, and a group consisting of nitrogen, phosphorus and arsenic. Of these, a group III-V nitride semiconductor layer composed of a group V element containing at least nitrogen can be formed.

  The metal material constituting the anode electrode may be appropriately selected according to the type of the III-V nitride semiconductor layer that forms the junction. For example, in the case of the nitride semiconductor layer described in the above embodiment, the metal material constituting the first anode electrode is not limited to Ti. For example, aluminum (Al), molybdenum (Mo), tantalum (Ta), tungsten ( Any metal that forms a Schottky barrier relatively lower than the second anode electrode, such as W) or silver (Ag), may be used. The metal material constituting the second anode electrode is not limited to Pt, and forms a Schottky barrier that is relatively higher than the first anode electrode, such as nickel (Ni), palladium (Pd), or Au (gold). What is necessary is just to select a metal. For use as a high-speed switching element, a combination is selected in which the Schottky barrier height of the first anode electrode is lower than 0.8 eV and the Schottky barrier height of the second anode electrode is higher than 0.8 eV. A high breakdown voltage characteristic is obtained with a low on-voltage, which is preferable.

  The substrate 1 may be a sapphire substrate or a silicon substrate instead of the silicon carbide substrate. In the case where a sapphire substrate is used, it is desirable to use gallium nitride (GaN) grown at a low temperature for the buffer layer 12.

  Although the low-temperature growth cap layer 16 of the present invention has been described as having a microcrystalline structure, this is an aggregate of microcrystalline grains or a rearranged structure thereof, and includes a growth temperature, an atmospheric gas composition during growth, and a substrate to be grown. Depending on the type of crystal, the size and arrangement of crystal grains vary and can be obtained by controlling the growth temperature within a range where desired insulation characteristics can be obtained. If the growth temperature of the third nitride semiconductor layer is set to a temperature lower by about 500 ° C. than the growth temperature of the second nitride semiconductor layer, a high Schottky barrier can be formed on the anode electrode, and the leakage current can be reduced. It is effective in reducing and improving reverse breakdown voltage. Furthermore, it is also suitable for suppressing current collapse.

It is explanatory drawing of the nitride semiconductor device which concerns on the 1st Example of this invention. It is a figure explaining the manufacturing method of the nitride semiconductor device concerning the 1st example of the present invention. It is explanatory drawing of the nitride semiconductor device which concerns on the 3rd Example of this invention. It is explanatory drawing of the nitride semiconductor device which concerns on the 4th Example of this invention.

Explanation of symbols

10: Schottky barrier diode, 11; substrate, 12; buffer layer, 13; channel layer, 14; Schottky layer, 16; cap layer, 16; low temperature growth cap layer, 17; 1st anode electrode, 20; 2nd anode electrode

Claims (5)

A III-group consisting of a Group III element consisting of at least one of the group consisting of gallium, aluminum, boron and indium and a Group V element containing at least nitrogen from the group consisting of nitrogen, phosphorus and arsenic on the substrate. A first group III-V nitride semiconductor layer made of a group V nitride semiconductor layer, and the group III-V nitride semiconductor layer stacked on the first group III-V nitride semiconductor layer; And a second group III-V nitride semiconductor layer that is laminated on the second group III-V nitride semiconductor layer, and the first and second group III-V nitride semiconductor layers are stacked on the second group III-V nitride semiconductor layer. A nitride semiconductor device in which a third group III-V nitride semiconductor layer made of a film having a deposition temperature lower than that of the group III-V nitride semiconductor layer is sequentially stacked;
A first anode electrode in which a part of the third and second group III-V nitride semiconductor layers is not formed in a concave shape and is Schottky-bonded to the first group III-V nitride semiconductor layer exposed in the recess. And a second anode electrode made of the same or different metal as the first anode electrode, and a Schottky junction to the third III-V nitride semiconductor layer and electrically connected to the first anode electrode, Prepared,
The height of the Schottky barrier at the junction formed between the first anode electrode and the first group III-V nitride semiconductor layer is determined by the second anode electrode and the third group III-V nitride. A nitride semiconductor device characterized by being lower than a height of a Schottky barrier of a junction formed between the metal semiconductor layer. A III-group consisting of a Group III element consisting of at least one of the group consisting of gallium, aluminum, boron and indium and a Group V element containing at least nitrogen from the group consisting of nitrogen, phosphorus and arsenic on the substrate. A first group III-V nitride semiconductor layer made of a group V nitride semiconductor layer, and the group III-V nitride semiconductor layer stacked on the first group III-V nitride semiconductor layer; And a second group III-V nitride semiconductor layer that is laminated on the second group III-V nitride semiconductor layer, and the first and second group III-V nitride semiconductor layers are stacked on the second group III-V nitride semiconductor layer. A nitride semiconductor device in which a third group III-V nitride semiconductor layer made of a film having a deposition temperature lower than that of the group III-V nitride semiconductor layer is sequentially stacked;
A first anode electrode that is Schottky-bonded to the third group III-V nitride semiconductor layer, and the third III layer other than a portion that is made of a metal different from the first anode electrode and is in contact with the first anode electrode. A Schottky junction to the group V nitride semiconductor layer and a second anode electrode electrically connected to the first anode electrode,
The height of the Schottky barrier at the junction formed between the first anode electrode and the third group III-V nitride semiconductor layer is determined by the second anode electrode and the third group III-V nitride. A nitride semiconductor device characterized by being lower than a height of a Schottky barrier of a junction formed between the metal semiconductor layer.   3. The nitride semiconductor device according to claim 1, wherein the third group III-V nitride semiconductor layer has a microcrystalline structure. 4.   4. The nitride semiconductor device according to claim 1, wherein an energy gap of the first group III-V nitride semiconductor layer is provided between the substrate and the first group III-V nitride semiconductor layer. A nitride semiconductor device comprising a fourth group III-V nitride semiconductor layer made of the group III-V nitride semiconductor having a smaller energy gap.   5. The nitride semiconductor device according to claim 1, wherein the second, third, and fourth group III-V nitride semiconductor layers are energy gaps of the first group III-V nitride semiconductor layer. A nitride semiconductor device having a smaller energy gap.

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