# US 2017/0288052 A1 · Multiple Shielding Trench Gate FET

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- Number: US 2017/0288052 A1
- Document ID: US20170288052A1
- Status: Published application
- Kind: A1
- Application number: 15/622,869
- Filed: 2017-06-14
- Published: 2017-10-05
- Earliest claimed: 2015-05-07
- Assignees: Texas Instruments Incorporated
- Applicants: Texas Instruments Incorporated
- Inventors: Hideaki Kawahara; Seetharaman Sridhar; Christopher Boguslaw Kocon; Simon John Molloy; Hong Yang
- Web page: https://patentgrep.com/patent/US20170288052A1

## CPC

- H10D 30/668: {having trench gate electrodes, e.g. UMOS transistors}
- H10D 30/0297: {using recessing of the gate electrodes, e.g. to form trench gate electrodes}
- H10D 62/109: {Reduced surface field [RESURF] PN junction structures}
- H10D 62/115: {Dielectric isolations, e.g. air gaps}
- H10D 64/01324: {characterised by the sectional shape, e.g. T or inverted-T}
- H10D 64/112: {comprising multiple field plate segments}
- H10D 64/117: {Recessed field plates, e.g. trench field plates or buried field plates}
- H10D 64/2527: {for vertical devices wherein the source or drain electrodes are recessed in semiconductor bodies}
- H10D 64/513: {within recesses in the substrate, e.g. trench gates, groove gates or buried gates}
- H10D 64/516: {the thicknesses being non-uniform}
- H10D 64/685: {being perpendicular to the channel plane}
- H10D 62/393: {Body regions of DMOS transistors or IGBTs (cell layout of DMOS H10D62/127)}
- H10D 64/256: {for lateral devices wherein the source or drain electrodes are recessed in semiconductor bodies (source or drain electrodes of TFTs H10D30/673)}
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A semiconductor device contains a vertical MOS transistor having a trench gate in trenches extending through a vertical drift region to a drain region. The trenches have field plates under the gate; the field plates are adjacent to the drift region and have a plurality of segments. A dielectric liner in the trenches separating the field plates from the drift region has a thickness great than a gate dielectric layer between the gate and the body. The dielectric liner is thicker on a lower segment of the field plate, at a bottom of the trenches, than an upper segment, immediately under the gate. The trench gate may be electrically isolated from the field plates, or may be connected to the upper segment. The segments of the field plates may be electrically isolated from each other or may be connected to each other in the trenches.

## Claims

### Claim 1

A method, comprising:
defining a trench vertically into a body region and a vertical drift region of a substrate;
forming a first dielectric liner on a sidewall of the trench, the first dielectric liner having a first thickness against the sidewall;
forming a second dielectric liner on the sidewall and positioned above the first dielectric liner, the second dielectric liner having a second thickness less than the first thickness;
forming a field plate against the first and second dielectric liners, the field plate separated from the vertical drift region by the first and second dielectric liners; and
forming a trench gate in the trench and above the field plate.

### Claim 2 (depends on 1)

The method of claim 1, further comprising:
forming an isolation layer on the field plate to isolate the field plate from the trench gate.

### Claim 3 (depends on 1)

The method of claim 1, wherein the forming the trench gate includes forming the trench gate contiguously on the field plate.

### Claim 4 (depends on 1)

The method of claim 1, wherein the forming the field plate includes:
forming a lower field plate segment having a first width; and
forming an upper field plate segment above the lower field plate segment, the upper field plate segment having a second width greater than the first width.

### Claim 5 (depends on 4)

The method of claim 4, wherein the forming the upper field plate segment includes forming the upper field plate segment contiguously on the lower field plate segment.

### Claim 6 (depends on 4)

The method of claim 4, further comprising:
forming an isolation layer on the lower field plate segment to isolate the lower field plate segment from the upper field plate segment.

### Claim 7 (depends on 1)

The method of claim 1, further comprising:
forming a gate dielectric layer against the sidewall to separate the trench gate from the body region, the gate dielectric layer having a third thickness less than the second thickness of the second dielectric liner.

### Claim 8 (depends on 1)

The method of claim 1, wherein:
the forming the first dielectric liner includes forming a first thermal oxide layer against the sidewall of the trench and having a third thickness less than the first thickness and the second thickness; and
the forming the second dielectric liner includes forming a second thermal oxide layer contiguous with the first thermal oxide layer and having the third thickness.

### Claim 9 (depends on 8)

The method of claim 8, wherein:
the forming the first dielectric liner includes forming a first silicon dioxide layer on the first thermal oxide layer and having a fourth thickness less than the first thickness and the second thickness; and
the forming the second dielectric liner includes forming a second silicon dioxide layer contiguous with the first silicon dioxide layer and having a fifth thickness less than the fourth thickness.

### Claim 10 (depends on 1)

The method of claim 1, further comprising:
forming a source region positioned above the body region and adjacent to the trench, the source region electrically coupled to the field plate; and
forming a drain region positioned under the vertical drift region, the drain region spaced apart from the trench.

### Claim 11

A method, comprising:
forming a vertical drift region;
forming a body region above the vertical drift region
forming a trench vertically into the body region and the vertical drift region;
forming a trench gate in the trench and adjacent to the body region;
forming a field plate in the trench and adjacent to the vertical drift region;
forming a first dielectric liner disposed on a sidewall of the trench and separating the field plate from the vertical drift region, the first dielectric liner having a first thickness; and
forming a second dielectric liner disposed on the sidewall and positioned above the first dielectric liner, the second dielectric liner separating the field plate from the vertical drift region and having a second thickness less than the first thickness.

### Claim 12 (depends on 11)

The method of claim 11, further comprising:
forming an isolation layer between the field plate and the trench gate, the isolation layer isolating the field plate from the trench gate.

### Claim 13 (depends on 11)

The method of claim 11, wherein the field plate is contiguous with the trench gate.

### Claim 14 (depends on 11)

The method of claim 11, wherein:
the field plate has a first width associated with a lower segment and a second width associated with an upper segment; and
the first width is less than the second width.

### Claim 15 (depends on 14)

The method of claim 14, wherein the lower segment is contiguous with the upper segment.

### Claim 16 (depends on 14)

The method of claim 14, further comprising:
forming an isolation layer between the lower segment and the upper segment and isolating the lower segment from the upper segment.

### Claim 17 (depends on 11)

The method of claim 11, further comprising:
forming a gate dielectric layer on the sidewall and separating the trench gate from the body region, the gate dielectric layer having a third thickness less than the second thickness of the second dielectric liner.

### Claim 18 (depends on 11)

The method of claim 11, wherein:
the first dielectric liner includes a first thermal oxide layer disposed on the sidewall of the trench and having a third thickness less than the first thickness and the second thickness; and
the second dielectric liner includes a second thermal oxide layer contiguous with the first thermal oxide layer and having the third thickness.

### Claim 19 (depends on 18)

The method of claim 18, wherein:
the first dielectric liner includes a first silicon dioxide layer disposed on the first thermal oxide layer and having a fourth thickness less than the first thickness and the second thickness; and
the second dielectric liner includes a second silicon dioxide layer contiguous with the first silicon dioxide layer and having a fifth thickness less than the fourth thickness.

### Claim 20 (depends on 11)

The method of claim 11, further comprising:
forming a source region above the body region and adjacent to the trench, the source region electrically coupled to the field plate; and
forming a drain region under the vertical drift region, the drain region spaced apart from the trench.