# US 8,772,785 B2 · Semiconductor device, schottky barrier diode, electronic apparatus, and method of producing semiconductor device

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- Number: US 8,772,785 B2
- Document ID: US8772785B2
- Status: Granted
- Kind: B2
- Application number: 13/141,448
- Filed: 2009-11-26
- Published: 2011-12-08
- Granted: 2014-07-08
- Earliest claimed: 2008-12-26
- Assignees: Renesas Electronics Corporation
- Applicants: Yasuhiro Okamoto; Hironobu Miyamoto; Yuji Ando; Tatsuo Nakayama; Takashi Inoue; Kazuki Ota; Kazuomi Endo
- Inventors: Yasuhiro Okamoto; Hironobu Miyamoto; Yuji Ando; Tatsuo Nakayama; Takashi Inoue; Kazuki Ota; Kazuomi Endo
- Web page: https://patentgrep.com/patent/US8772785B2

## CPC

- H10D 8/60: Schottky-barrier diodes
- H10D 30/6738: {Schottky barrier electrodes}
- H10D 30/675: {Group III-V materials, Group II-VI materials, Group IV-VI materials, selenium or tellurium}
- H10D 62/13: Semiconductor regions connected to electrodes carrying current to be rectified, amplified or switched, e.g. source or drain regions
- H10D 62/85: being Group III-V materials, e.g. GaAs
- H10D 62/8503: {Nitride Group III-V materials, e.g. AlN or GaN}
- H10D 64/64: Electrodes comprising a Schottky barrier to a semiconductor
- H10D 62/852: being Group III-V materials comprising three or more elements, e.g. AlGaN or InAsSbP
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A semiconductor device includes semiconductor layers, an anode electrode, and a cathode electrode. The semiconductor layers include a composition change layer, the anode electrode is electrically connected to one of principal surfaces of the composition change layer through a formation of a Schottky junction between the anode electrode and a part of the semiconductor layers, the cathode electrode is electrically connected to the other of the principal surfaces of the composition change layer through a formation of a junction between the cathode electrode and another part of the semiconductor layers, the anode electrode and the cathode electrode are capable of applying a voltage to the composition change layer in a direction perpendicular to the principal surface.

## Claims

### Claim 1

A semiconductor device comprising:
semiconductor layers;
an anode electrode; and
a cathode electrode, wherein
the semiconductor layers include a composition change layer,
the anode electrode is electrically connected to one of principal surfaces of the composition change layer through a formation of a Schottky junction between the anode electrode and a part of the semiconductor layers,
the cathode electrode is electrically connected to the other of the principal surfaces of the composition change layer through a formation of a junction between the cathode electrode and another part of the semiconductor layers,
the anode electrode and the cathode electrode are capable of applying a voltage to the composition change layer in a direction perpendicular to the principal surface, and
the composition change layer has composition that changes from a cathode electrode side toward an anode electrode side in the direction perpendicular to the principal surface of the composition change layer, has a negative polarization charge that is generated due to the composition that changes, and contains a donor impurity.

### Claim 2 (depends on 1)

The semiconductor device according to claim 1, wherein the semiconductor layers are formed of a nitride semiconductor.

### Claim 3 (depends on 2)

The semiconductor device according to claim 2, wherein the semiconductor layers are formed of a III-nitride semiconductor.

### Claim 4 (depends on 1)

The semiconductor device according to claim 1, wherein the composition change layer has composition represented by AlxGa1-xN (0≦x<1), and a relationship between an Al composition ratio at the principal surface at the cathode electrode side x0 (x0>0) and an Al composition ratio at the principal surface at the anode electrode side xA (xA≧0) satisfies the following equation: x0>xA.

### Claim 5 (depends on 4)

The semiconductor device according to claim 4, wherein an Al composition ratio x of the composition change layer decreases continuously from x0 to xA from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition change layer.

### Claim 6 (depends on 4)

The semiconductor device according to claim 4, wherein an Al composition ratio x of the composition change layer decreases in a stepwise manner from x0 to xA from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition change layer.

### Claim 7 (depends on 5)

The semiconductor device according to claim 5, wherein a decreasing gradient of the Al composition ratio of the composition change layer is a steep gradient from the cathode electrode side toward the anode electrode side.

### Claim 8 (depends on 7)

The semiconductor device according to claim 7, wherein a volume density of a polarization charge that is generated in the composition change layer is uniform over the entire composition change layer.

### Claim 9 (depends on 5)

The semiconductor device according to claim 5, wherein a volume density of a polarization charge that is generated in the composition change layer decreases from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition, change layer.

### Claim 10 (depends on 9)

The semiconductor device according to claim 9, wherein a donor impurity concentration in the composition change layer decreases from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition change layer.

### Claim 11 (depends on 9)

The semiconductor device according to claim 9, wherein a donor impurity concentration in the composition change layer is uniform over the entire composition change layer.

### Claim 12 (depends on 1)

The semiconductor device according to claim 1, wherein a donor impurity concentration (m−3) in the composition change layer is equal to a maximum value NPOLMAX (m−3) of a volume density of a polarization charge that can be generated in the composition change layer.

### Claim 13 (depends on 1)

The semiconductor device according to claim 1, wherein a donor impurity concentration (m−3) in the composition change layer is not more than 5 times the maximum value NPOLMAX (m−3) of a volume density of a polarization charge that can be generated in the composition change layer.

### Claim 14 (depends on 1)

The semiconductor device according to claim 1, wherein a donor impurity concentration (m−3) in the composition change layer is not more than 2.5 times the maximum value NPOLMAX (m−3) of a volume density of a polarization charge that can be generated in the composition change layer.

### Claim 15 (depends on 1)

The semiconductor device according to claim 1, wherein a junction plane between the cathode electrode and the semiconductor layer and the principal surface of the composition change layer at the cathode electrode side are arranged on the same level.

### Claim 16 (depends on 1)

The semiconductor device according to claim 1, wherein the cathode electrode is formed at a top surface side of the semiconductor layer.

### Claim 17 (depends on 1)

The semiconductor device according to claim 1, wherein the cathode electrode is formed at a bottom surface side of the semiconductor layer.

### Claim 18 (depends on 1)

The semiconductor device according to claim 1, wherein the cathode electrode is in ohmic contact with the semiconductor layer.

### Claim 19 (depends on 1)

The semiconductor device according to claim 1, further comprising:
an insulation film, wherein
an opening portion to be filled is formed at a part of a junction part of the semiconductor layer where it forms a junction with the anode electrode,
the insulation film is formed so as to cover the opening portion to be filled, and
the anode electrode forms a junction with the opening portion to be filled via the insulation film and forms a Schottky junction with a part of the junction part excluding the opening portion to be filled.

### Claim 20 (depends on 19)

The semiconductor device according to claim 19, wherein a bottom surface of the composition change layer is arranged on the same level as or on a higher level than a lower end of the opening portion to be filled.

### Claim 21 (depends on 19)

The semiconductor device according to claim 19, wherein a top surface of the composition change layer is arranged on a lower level than an upper end of the opening portion to be filled.

### Claim 22 (depends on 21)

The semiconductor device according to claim 21, wherein the top surface of the composition change layer is arranged on the same level as or on a lower level than a lower end of the opening portion to be filled.

### Claim 23 (depends on 1)

The semiconductor device according to claim 1, wherein the semiconductor device is a Schottky barrier diode.

### Claim 24 (depends on 1)

An electronic apparatus comprising the semiconductor device according to claim 1.

### Claim 25 (depends on 1)

A method of producing the semiconductor device according to claim 1 comprising:
a semiconductor layer formation step of forming the semiconductor layers; and
an electrode junction step of forming a Schottky junction between the anode electrode and a part of the semiconductor layers and of forming a junction between the cathode electrode and another part of the semiconductor layers, wherein the semiconductor layer formation step comprises a composition change layer formation step,
in the composition change layer formation step, the composition change layer is formed such that it generates a negative polarization charge due to its composition that changes in the direction perpendicular to the principal surface and it contains a donor impurity, and
in the electrode junction step, the anode electrode and the cathode electrode are formed so as to be capable of applying a voltage to the composition change layer in the direction perpendicular to the principal surface.

### Claim 26 (depends on 5)

A method of producing the semiconductor device according to claim 5 comprising:
a semiconductor layer formation step of forming the semiconductor layers; and
an electrode junction step of forming a Schottky junction between the anode electrode and a part of the semiconductor layers and of forming a junction between the cathode electrode and another part of the semiconductor layers, wherein the semiconductor layer formation step comprises a composition change layer formation step,
in the composition change layer formation step, the composition change layer is formed such that it generates a negative polarization charge due to its composition that changes in the direction perpendicular to the principal surface and it contains a donor impurity, and
in the electrode junction step, the anode electrode and the cathode electrode are formed so as to be capable of applying a voltage to the composition change layer in the direction perpendicular to the principal surface, and wherein
in the composition change layer formation step, the composition change layer is formed such that the Al composition ratio x of the composition change layer decreases continuously from x0 to xA from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition change layer.

### Claim 27 (depends on 6)

A method of producing the semiconductor device according to claim 6 comprising:
a semiconductor layer formation step of forming the semiconductor layers; and
an electrode junction step of forming a Schottky junction between the anode electrode and a part of the semiconductor layers and of forming a junction between the cathode electrode and another part of the semiconductor layers, wherein the semiconductor layer formation step comprises a composition change layer formation step,
in the composition change layer formation step, the composition change layer is formed such that it generates a negative polarization charge due to its composition that changes in the direction perpendicular to the principal surface and it contains a donor impurity, and
in the electrode junction step, the anode electrode and the cathode electrode are formed so as to be capable of applying a voltage to the composition change layer in the direction perpendicular to the principal surface, and wherein
in the composition change layer formation step, the composition change layer is formed such that the Al composition ratio x of the composition change layer decreases in a stepwise manner from x0 to xA from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition change layer.

### Claim 28 (depends on 7)

A method of producing the semiconductor device according to claim 7 comprising:
a semiconductor layer formation step of forming the semiconductor layers; and
an electrode junction step of forming a Schottky junction between the anode electrode and a part of the semiconductor layers and of forming a junction between the cathode electrode and another part of the semiconductor layers, wherein the semiconductor layer formation step comprises a composition change layer formation step,
in the composition change layer formation step, the composition change layer is formed such that it generates a negative polarization charge due to its composition that changes in the direction perpendicular to the principal surface and it contains a donor impurity, and
in the electrode junction step, the anode electrode and the cathode electrode are formed so as to be capable of applying a voltage to the composition change layer in the direction perpendicular to the principal surface, and wherein
in the composition change layer formation step, the composition change layer is formed such that the Al composition ratio x of the composition change layer decreases continuously from x0 to xA from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition change layer, and the decreasing gradient of the Al composition ratio of the composition change layer is a steep gradient from the cathode electrode side toward the anode electrode side.

### Claim 29 (depends on 8)

A method of producing the semiconductor device according to claim 8 comprising:
a semiconductor layer formation step of forming the semiconductor layers; and
an electrode junction step of forming a Schottky junction between the anode electrode and a part of the semiconductor layers and of forming a junction between the cathode electrode and another part of the semiconductor layers, wherein the semiconductor layer formation step comprises a composition change layer formation step,
in the composition change layer formation step, the composition change layer is formed such that it generates a negative polarization charge due to its composition that changes in the direction perpendicular to the principal surface and it contains a donor impurity, and
in the electrode junction step, the anode electrode and the cathode electrode are formed so as to be capable of applying a voltage to the composition change layer in the direction perpendicular to the principal surface, and wherein
in the composition change layer formation step, the composition change layer is formed such that the Al composition ratio x of the composition change layer decreases continuously from x0 to xA from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition change layer, the decreasing gradient of the Al composition ratio of the composition change layer is a steep gradient from the cathode electrode side toward the anode electrode side, and a volume density of a polarization charge that is generated in the composition change layer is uniform over the entire composition change layer.

### Claim 30 (depends on 19)

A method of producing the semiconductor device according to claim 19 comprising:
a semiconductor layer formation step of forming the semiconductor layers; and
an electrode junction step of forming a Schottky junction between the anode electrode and a part of the semiconductor layers and of forming a junction between the cathode electrode and another part of the semiconductor layers,
an opening portion to be filled formation step of forming the opening portion to be filled on a part of the semiconductor layer; and
an insulation film formation step of forming the insulation film so as to cover the opening portion to be filled, wherein
the semiconductor layer formation step comprises a composition change layer formation step,
in the composition change layer formation step, the composition change layer is formed such that it generates a negative polarization charge due to its composition that changes in the direction perpendicular to the principal surface and it contains a donor impurity, and
in the electrode junction step, the anode electrode and the cathode electrode are formed so as to be capable of applying a voltage to the composition change layer in the direction perpendicular to the principal surface, and wherein
in the electrode junction step, the anode electrode forms a junction with the opening portion to be filled via the insulation film and forms a Schottky junction with a part of the junction part excluding the opening portion to be filled.

### Claim 31 (depends on 1)

The semiconductor device according to claim 1, wherein the composition change layer has composition represented by AlxGa1-xN (0≦x<1), and a relationship between an Al composition ratio at the principal surface at the cathode electrode side x0 (x0>0) and an Al composition ratio at the principal surface at the anode electrode side xA (xA≧0) satisfies the following equation: x0>xA;
wherein an Al composition ratio x of the composition change layer decreases in a stepwise manner from x0 to xA from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition change layer; and
wherein a decreasing gradient of the Al composition ratio of the composition change layer is a steep gradient from the cathode electrode side toward the anode electrode side.

### Claim 32 (depends on 1)

The semiconductor device according to claim 1, wherein the composition change layer has composition represented by AlxGa1-xN (0≦x<1), and a relationship between an Al composition ratio at the principal surface at the cathode electrode side x0 (x0>0) and an Al composition ratio at the principal surface at the anode electrode side xA (xA≧0) satisfies the following equation: x0>xA;
wherein an Al composition ratio x of the composition change layer decreases in a stepwise manner from x0 to xA from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition change layer;
wherein a volume density of a polarization charge that is generated in the composition change layer decreases from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition, change layer;
wherein a decreasing gradient of the Al composition ratio of the composition change layer is a steep gradient from the cathode electrode side toward the anode electrode side; and
wherein a volume density of a polarization charge that is generated in the composition change layer is uniform over the entire composition change layer.

### Claim 33 (depends on 1)

The semiconductor device according to claim 1, wherein the composition change layer has composition represented by AlxGa1-xN (0≦x<1), and a relationship between an Al composition ratio at the principal surface at the cathode electrode side x0 (x0>0) and an Al composition ratio at the principal surface at the anode electrode side xA (xA≧0) satisfies the following equation: x0>xA;
wherein an Al composition ratio x of the composition change layer decreases in a stepwise manner from x0 to xA from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition change layer;
wherein a volume density of a polarization charge that is generated in the composition change layer decreases from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition, change layer; and
wherein a donor impurity concentration in the composition change layer decreases from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition change layer.

### Claim 34

A method of producing a semiconductor device comprising semiconductor layers, an anode electrode, and a cathode electrode, wherein the semiconductor layers include a composition change layer, the anode electrode is electrically connected to one of principal surfaces of the composition change layer through a formation of a Schottky junction between the anode electrode and a part of the semiconductor layers, the cathode electrode is electrically connected to the other of the principal surfaces of the composition change layer through a formation of a junction between the cathode electrode and another part of the semiconductor layers, the anode electrode and the cathode electrode are capable of applying a voltage to the composition change layer in a direction perpendicular to the principal surface,
the composition change layer has composition that changes from a cathode electrode side toward an anode electrode side in the direction perpendicular to the principal surface of the composition change layer, has a negative polarization charge that is generated due to the composition that changes, and contains a donor impurity;
the method comprising:
a semiconductor layer formation step of forming the semiconductor layers; and an electrode junction step of forming a Schottky junction between the anode electrode and a part of the semiconductor layers and of forming a junction between the cathode electrode and another part of the semiconductor layers, wherein the semiconductor layer formation step comprises a composition change layer formation step,
in the composition change layer formation step, the composition change layer is formed such that it generates a negative polarization charge due to its composition that changes in the direction perpendicular to the principal surface and it contains a donor impurity, and
in the electrode junction step, the anode electrode and the cathode electrode are formed so as to be capable of applying a voltage to the composition change layer in the direction perpendicular to the principal surface; and
wherein in the composition change layer formation step, the composition change layer is formed such that the Al composition ratio x of the composition change layer decreases continuously from x0 to xA from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition change layer; and
wherein in the composition change layer formation step, the composition change layer is formed such that the Al composition ratio x of the composition change layer decreases continuously from x0 to xA from the cathode electrode side toward the anode electrode side in the direction perpendicular to the principal surface of the composition change layer, and the decreasing gradient of the Al composition ratio of the composition change layer is a steep gradient from the cathode electrode side toward the anode electrode side.

### Claim 35 (depends on 34)

A method of producing a semiconductor device according to claim 34, wherein a volume density of a polarization charge that is generated in the composition change layer is uniform over the entire composition change layer.