# US 12,009,390 B2 · Vertical MOSFET having a high resistance region

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- Number: US 12,009,390 B2
- Document ID: US12009390B2
- Status: Granted
- Kind: B2
- Application number: 17/709,383
- Filed: 2022-03-30
- Published: 2022-07-14
- Granted: 2024-06-11
- Earliest claimed: 2016-08-24
- Assignees: Fuji Electric Co., Ltd.
- Applicants: Fuji Electric Co., Ltd.
- Inventors: Katsunori Ueno
- Web page: https://patentgrep.com/patent/US12009390B2

## CPC

- H10D 62/109: {Reduced surface field [RESURF] PN junction structures}
- H10D 12/031: {of IGBTs}
- H10D 30/0291: {of vertical DMOS [VDMOS] FETs}
- H10D 30/0297: {using recessing of the gate electrodes, e.g. to form trench gate electrodes}
- H10D 30/66: Vertical DMOS [VDMOS] FETs
- H10D 30/668: {having trench gate electrodes, e.g. UMOS transistors}
- H10D 62/107: {Buried supplementary regions, e.g. buried guard rings (multi-RESURF H10D62/111)}
- H10D 62/157: {Impurity concentrations or distributions}
- H10D 62/393: {Body regions of DMOS transistors or IGBTs (cell layout of DMOS H10D62/127)}
- H10D 62/8325: {Silicon carbide}
- H10D 62/8503: {Nitride Group III-V materials, e.g. AlN or GaN}
- H10P 30/2042: {into crystalline silicon carbide}
- H10P 30/206: {into Group III-V semiconductors}
- H10P 30/21: {of electrically active species}
- H10P 30/218: {characterised by the implantation in a compound semiconductor of both electrically active and inactive species in the same semiconductor region to be doped n-type or p-type}
- H10P 30/28: characterised by an annealing step, e.g. for activation of dopants
- H10P 95/904: {of Group III-V semiconductors}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

A vertical MOSFET having a compound semiconductor layer is provided, the vertical MOSFET comprising a gate electrode, a gate insulating film provided between the gate electrode and the compound semiconductor layer, a drift region provided directly in contact with at least a part of the gate insulating film and being a part of the compound semiconductor layer, and a high resistance region provided at least in the drift region, is positioned below at least a part of the gate insulating film, and has a higher resistance value per unit length than that of the drift region.

## Claims

### Claim 1

A vertical MOSFET having a compound semiconductor layer, the vertical MOSFET comprising:
a gate electrode;
a gate insulating film which is provided between the gate electrode and the compound semiconductor layer;
a drift region which is provided directly in contact with at least a part of the gate insulating film and is a part of the compound semiconductor layer; and
a high resistance region which is provided at least in the drift region, is positioned below at least the part of the gate insulating film, and has a higher resistance value per unit length than that of the drift region, wherein
the gate electrode is a trench type gate electrode which is embedded in a trench portion that is provided in the compound semiconductor layer,
the high resistance region is adjacent to a bottom portion of the trench portion,
the high resistance region is spaced from the gate insulating film and below at least the part of the gate insulating film,
a width of the high resistance region is wider than a width of the trench portion,
the high resistance region has a resistance value of equal to or more than 10 Ω·cm per unit length, and
the compound semiconductor layer is a gallium nitride layer.

### Claim 2 (depends on 1)

The vertical MOSFET according to claim 1, wherein
the resistance value per unit length of the high resistance region is higher than a resistance value per unit length of a base region which is a part of the compound semiconductor layer.

### Claim 3 (depends on 1)

The vertical MOSFET according to claim 1, wherein
the high resistance region has a resistance-increasing element with a concentration of equal to or more than 1E+16 cm−3 and equal to or less than 1E+19 cm−3.

### Claim 4 (depends on 3)

The vertical MOSFET according to claim 3, wherein
the resistance-increasing element is different from an impurity element which forms majority carriers in the drift region.

### Claim 5 (depends on 3)

The vertical MOSFET according to claim 3, wherein
the resistance-increasing element is an impurity element which is the same as an impurity element forming majority carriers in a base region that is a part of the compound semiconductor layer.

### Claim 6

A vertical MOSFET having a gallium nitride layer, the vertical MOSFET comprising:
a gate electrode;
a gate insulating film which is provided between the gate electrode and the gallium nitride layer;
a drift region which is provided directly in contact with at least a part of the gate insulating film and is a part of the gallium nitride layer; and
a high resistance region which is provided at least in the drift region, is positioned below at least the part of the gate insulating film, and has a higher resistance value per unit length than that of the drift region and is a part of the gallium nitride layer, wherein
the gate electrode is a trench type gate electrode which is embedded in a trench portion that is provided in the gallium nitride layer,
the high resistance region is adjacent to a bottom portion of the trench portion,
a width of the high resistance region is wider than a width of the trench portion,
the high resistance region has a resistance value of equal to or more than 10 Ωcm per unit length,
the high resistance region has a resistance-increasing element with a concentration of equal to or more than 1E+16 cm−3 and equal to or less than 1E+19 cm−3,
the high resistance region is formed by annealing at a temperature of equal to or more than 1000° C. and equal to or less than 1300° C. after implantation of the resistance-increasing element, the annealing performed before the gate insulating film is provided,
the resistance-increasing element is one or more of magnesium, argon, and nitrogen,
the high resistance region is provided separate from the bottom portion of the trench portion and below the bottom portion, and has electrical characteristics of an insulator, and
sides of the trench portion are mainly in contact with a base region.

### Claim 7 (depends on 6)

The vertical MOSFET according to claim 6, wherein
the resistance value per unit length of the high resistance region is higher than a resistance value per unit length of the base region which is a part of the gallium nitride layer.

### Claim 8 (depends on 6)

The vertical MOSFET according to claim 6, wherein
the resistance-increasing element is different from an impurity element which forms majority carriers in the drift region.

### Claim 9 (depends on 6)

The vertical MOSFET according to claim 6, wherein
the resistance-increasing element is an impurity element which is the same as an impurity element forming majority carriers in the base region that is a part of the gallium nitride layer.

### Claim 10 (depends on 6)

The vertical MOSFET according to claim 6, wherein
the resistance-increasing element is magnesium.

### Claim 11 (depends on 6)

The vertical MOSFET according to claim 6, wherein
the gate electrode extends above a front surface of the gallium nitride layer.