# US 7,745,845 B2 · Integrated low leakage schottky diode

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- Number: US 7,745,845 B2
- Document ID: US7745845B2
- Status: Granted
- Kind: B2
- Application number: 12/107,995
- Filed: 2008-04-23
- Published: 2009-10-29
- Granted: 2010-06-29
- Earliest claimed: 2008-04-23
- Assignees: Fairchild Semiconductor Corporation
- Inventors: Jun Cai
- Web page: https://patentgrep.com/patent/US7745845B2

## CPC

- H10D 8/00: Diodes (variable-capacitance diodes H10D1/64; gated diodes H10D12/00)
- H10D 8/051: {of Schottky diodes}
- H10D 8/20: Breakdown diodes, e.g. avalanche diodes
- H10D 8/60: Schottky-barrier diodes
- H10D 62/17: Semiconductor regions connected to electrodes not carrying current to be rectified, amplified or switched, e.g. channel regions
- H10D 62/108: {having localised breakdown regions, e.g. built-in avalanching regions (in self-protected thyristors H10D18/211)}
- H10D 64/111: {Field plates}
- H10D 64/64: Electrodes comprising a Schottky barrier to a semiconductor
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

An integrated low leakage Schottky diode has a Schottky barrier junction proximate one side of an MOS gate with one end of a drift region on an opposite side of the gate. Below the Schottky metal and the gate oxide is a RESURF structure of an N− layer over a P− layer which also forms the drift region that ends at the diode's cathode in one embodiment of the present invention. The N− and P− layers have an upward concave shape under the gate. The gate electrode and the Schottky metal are connected to the diode's anode. A P− layer lies between the RESURF structure and an NISO region which has an electrical connection to the anode. A P+ layer under the Schottky metal is in contact with the P− layer through a P well.

## Claims

### Claim 1

A diode having an anode and a cathode comprising:
a metal portion of a Schottky barrier junction coupled to said anode or said cathode;
an insulated gate having one side thereof adjacent said metal portion and having an electrode electrically coupled to said metal portion, said insulated gate having a concave-shaped conduction channel; and
a first end of a drift region adjacent an opposite side of said gate with a second end of said drift region coupled to said cathode if said metal portion is connected to said anode, and to said anode if said metal portion is connected to said cathode.

### Claim 2 (depends on 1)

The diode set forth in claim 1 further including a first layer of a first conductivity type under a gate oxide of said gate.

### Claim 3 (depends on 2)

The diode set forth in claim 2 further including a second layer of a second conductivity type under, and in contact with, said first layer.

### Claim 4 (depends on 3)

The diode set forth in claim 3 wherein said first layer and said second layer form a RESURF structure.

### Claim 5 (depends on 2)

The diode set forth in claim 2 further including a first region of said second conductivity type in contact with said metal portion and said first layer.

### Claim 6 (depends on 5)

The diode set forth in claim 5 further including a well of said second conductivity type in contact with said first region.

### Claim 7 (depends on 6)

The diode set forth in claim 6 further including a second region in contact with said well and said second layer.

### Claim 8 (depends on 7)

The diode set forth in claim 7 further including an isolation region of said first conductivity type under, and in contact with, said second region, said isolation region electrically coupled to said metal.

### Claim 9 (depends on 3)

The diode set forth in claim 3 wherein said first layer and said second layer form a concave-shaped conduction channel under said gate.

### Claim 10 (depends on 8)

The diode set forth in claim 8 wherein said isolation region, said second region, said second layer, and said first layer form a parasitic bipolar transistor which conducts current from said anode to said cathode.

### Claim 11 (depends on 1)

The diode set forth in claim 1 wherein said gate is the gate of a punch-through MOSFET.

### Claim 12

A diode having an anode and a cathode comprising:
a metal portion of a Schottky barrier junction coupled to said anode;
an insulated gate having one side thereof adjacent said metal portion and having an electrode electrically coupled to said anode, said insulated gate positioned between said metal portion and said cathode;
a first layer of a first conductivity type in contact with said cathode;
a plurality of regions of a second conductivity type opposite said first conductivity type which are connected together and coupled to said anode, wherein at least one of said plurality of regions is in contact with said first layer; and
a second layer of said first conductivity type coupled to said anode and in contact with at least one of said plurality of regions;
wherein said second layer forms a collector, said at least one of said plurality of regions forms a base, and said first layer forms an emitter of a parasitic NPN transistor.

### Claim 13

A diode having an anode and a cathode comprising:
a metal portion of a Schottky barrier junction coupled to said anode or said cathode;
an insulated gate having one side thereof adjacent said metal portion and having an electrode electrically coupled to said metal portion;
a first end of a drift region adjacent an opposite side of said gate with a second end of said drift region coupled to said cathode if said metal portion is connected to said anode, and to said anode if said metal portion is connected to said cathode; and
a layer having a substantially flat upper surface in contact with said metal portion and said gate oxide and extending into said drift region.

### Claim 14

A diode having an anode and a cathode comprising:
a metal portion of a Schottky barrier junction coupled to said anode or said cathode;
an insulated gate with a split level gate oxide, said insulated gate having one side thereof adjacent said metal portion and having an electrode electrically coupled to said metal portion; and
a first end of a drift region adjacent an opposite side of said gate with a second end of said drift region coupled to said cathode if said metal portion is connected to said anode, and to said anode if said metal portion is connected to said cathode.

### Claim 15

A method of forming a diode having an anode and a cathode comprising:
forming a metal portion of a Schottky barrier junction that is coupled to said anode or said cathode;
forming an insulated gate having one side thereof adjacent said metal portion and having an electrode electrically coupled to said metal portion;
forming a concave-shaped conduction channel under said insulated gate; and
forming a first end of a drift region adjacent an opposite side of said gate with a second end of said drift region coupled to said cathode if said metal portion is connected to said anode, and to said anode if said metal portion is connected to said cathode.

### Claim 16 (depends on 15)

The method set forth in claim 15 further including forming a first layer of a first conductivity type under a gate oxide of said gate.

### Claim 17 (depends on 16)

The method set forth in claim 16 further including forming a second layer of a second conductivity type under, and in contact with, said first layer.

### Claim 18 (depends on 17)

The method set forth in claim 17 wherein said first layer and said second layer form a RESURF structure.

### Claim 19 (depends on 16)

The method set forth in claim 16 further including forming a first region of said second conductivity type in contact with said metal portion and said first layer.

### Claim 20 (depends on 19)

The method set forth in claim 19 further including forming a well of said second conductivity type in contact with said first region.