SEMICONDUCTOR DEVICE

• US 20160181413A1
• Filed: 10/09/2015
• Published: 06/23/2016
• Est. Priority Date: 12/17/2014
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: FUJITA, Koichi
• Granted Patent: US 10,256,336 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H01L 29/0607 for preventing surface leakage or controlling electric field concentration
• CPC Class Codes: H01L 29/1095 Body region, i.e. base region, of DMOS transistors or IGBTs cell layout H01L29/0696
• CPC Class Codes: H01L 29/402 Field plates
• CPC Class Codes: H01L 29/407 Recessed field plates, e.g. trench field plates, buried field plates
• CPC Class Codes: H01L 29/41 characterised by their shape, relative sizes or dispositions
• CPC Class Codes: H01L 29/41766 with at least part of the source or drain electrode having contact below the semiconductor surface, e.g. the source or drain electrode formed at least partially in a groove or with inclusions of conductor inside the semiconductor H01L29/41733 - H01L29/41758 take precedence
• CPC Class Codes: H01L 29/41775 characterised by the proximity or the relative position of the source or drain electrode and the gate electrode, e.g. the source or drain electrode separated from the gate electrode by side-walls or spreading around or above the gate electrode
• CPC Class Codes: H01L 29/66696 with a step of recessing the source electrode
• CPC Class Codes: H01L 29/7395 Vertical transistors, e.g. vertical IGBT
• CPC Class Codes: H01L 29/7802 Vertical DMOS transistors, i.e. VDMOS transistors
• CPC Class Codes: H01L 29/7816 Lateral DMOS transistors, i.e. LDMOS transistors

Abstract

A semiconductor device is provided with an N⁻-type drift layer, a N⁺-type diffusion well region provided on a surface part of the N⁻-type drift layer, a P-type channel well region, an N⁺-type diffusion well region, a gate insulating film, a gate electrode laminated on the gate insulating film, a drain trench, a field plate provided in the drain trench with a silicon oxide film and an insulating film interposed therebetween and a field plate electrode formed on the field plate. The field plate is tapered toward a base part of the drain trench. A distance between a side wall of the drain trench and a side face of the field plate is increased toward the base part side.

Claims

1. A semiconductor device comprising:

a drift layer made of a first conductive type semiconductor;

a first electrode provided on a back side of the drift layer and electrically connected to the drift layer;

a first well region provided on a surface part of the drift layer and made of a semiconductor of a second conductive type opposite to the first conductive type;

a second well region provided on a surface part of the first well region and made of a semiconductor of the first conductive type;

a second electrode electrically connected to the second well region;

a gate electrode provided above the first and second well regions and the drift layer with a gate insulating film interposed between the gate electrode and the first and second well regions and the drift layer; and

a field plate embedded in a first trench formed adjacent to the gate electrode on the surface part of the drift layer with an insulating film interposed between the field plate and the first trench and insulated from the gate electrode,

wherein the first trench includes a base part and a side wall, the field plate is tapered toward the base part, and a distance between the side wall and a side face of the field plate is increased toward the base part side.

2. The semiconductor device according to claim 1, wherein the field plate is linearly tapered.

3. The semiconductor device according to claim 1, wherein the side face of the field plate is a curved surface.

4. The semiconductor device according to claim 1,

wherein

a second trench is provided in the first well region,

a third well region of the second conductive type is formed by implantation of an impurity into a base part of the second trench, and

the semiconductor device further comprises a trench electrode made of a conductive material embedded in the second trench and electrically connected to the second electrode.

5. The semiconductor device according to claim 4, wherein the second trench is deeper than the first trench.

6. The semiconductor device according to claim 4, further comprising a side face insulating film that covers a side face of the gate electrode,

wherein the trench electrode reaches the first well region from a position adjacent to the side face insulating film while contacting the second well region immediately below the side wall insulating film.

7. The semiconductor device according to claim 1, wherein a semiconductor layer of the second conductive type is provided between the drift layer and the first electrode.

8. The semiconductor device according to claim 4, wherein a semiconductor layer of the second conductive type is provided between the drift layer and the first electrode.

9. The semiconductor device according to claim 6, wherein a semiconductor layer of the second conductive type is provided between the drift layer and the first electrode.

10. A semiconductor device comprising:

a drift layer made of a first conductive type semiconductor;

a first electrode provided on a back side of the drift layer and electrically connected to the drift layer;

a first well region provided on a surface part of the drift layer and made of a semiconductor of a second conductive type opposite to the first conductive type;

a second well region provided on a surface part of the first well region and made of a semiconductor of the first conductive type;

a second electrode electrically connected to the second well region;

a gate electrode provided above the first and second well regions and the drift layer with a first insulating film interposed between the gate electrode and the first and second well regions and the drift layer; and

a field plate provided above the drift layer and adjacent to the gate electrode with a second insulating film interposed between the filed plate and the drift layer,

wherein a thickness of the second insulating film increases as the distance from the gate electrode increases.

11. The semiconductor device according to claim 10, wherein the second insulating film continuously becomes thicker as the distance from the gate electrode increases so as to be convex toward the field plate side.

12. The semiconductor device according to claim 11,

wherein the surface part of the drift layer comprises a concave part in a lower part of the field plate, and the concave part is caved in continuously deeper as the distance from the gate electrode increases, and

the second insulating film is provided between the concave part and the field plate.

13. The semiconductor device according to claim 12,

wherein the first insulating film and the second insulating film are one continuous film on the drift layer.

14. The semiconductor device according to claim 12,

wherein the second insulating film is a LOCOS oxide film formed by thermally oxidizing the drift layer.

15. The semiconductor device according to claim 10,

wherein the surface part of the drift layer comprises a concave part in a lower part of the field plate, and the concave part is caved in continuously deeper as the distance from the gate electrode increases, and

the second insulating film is provided between the concave part and the field plate.