Semiconductor device with graded drift region

• US 9,525,059 B1
• Filed: 03/02/2016
• Issued: 12/20/2016
• Est. Priority Date: 09/11/2015
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kobayashi, Kenya
• Primary Examiner(s): Bachner, Robert
• Application Number:
  US15/059,271
• Time in Patent Office: 293 Days
• US Class Current: 1/1
• CPC Class Codes: H01L 29/0878 Impurity concentration or distribution
• CPC Class Codes: H01L 29/407 Recessed field plates, e.g. trench field plates, buried field plates
• CPC Class Codes: H01L 29/42368 the thickness being non-uniform
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236

Abstract

A semiconductor device includes a semiconductor layer that has a first surface and a second surface, a drift region of a first conductivity type in the semiconductor layer, a body region of a second conductivity type between the drift region and the first surface, a source region of first conductivity type, a first gate electrode, a second gate electrode with the body region interposed between the first gate electrode and the second gate electrode, first and second gate insulating films, a first field plate electrode between the second surface and the first gate electrode, a second field plate electrode between the second surface and the second gate electrode, a first region of the first conductivity type in the drift region, a second region between the first region and the body region, and a third region between the second region and the body region.

Claims

1. A semiconductor device, comprising:

a semiconductor layer that has a first surface and a second surface;

a drift region of a first conductivity type in the semiconductor layer;

a body region of a second conductivity type in the semiconductor layer between the drift region and the first surface;

a source region of the first conductivity type in the semiconductor layer between the body region and the first surface;

a first gate electrode;

a second gate electrode, the body region being between the first gate electrode and the second gate electrode;

a first gate insulating film between the first gate electrode and the body region;

a second gate insulating film between the second gate electrode and the body region;

a first field plate electrode between the second surface and the first gate electrode;

a second field plate electrode between the second surface and the second gate electrode;

a first field plate insulating film between the first field plate electrode and the drift region;

a second field plate insulating film between the second field plate electrode and the drift region;

a first region of the drift region having at least a portion between the first field plate electrode and the second field plate electrode;

a second region of the drift region between the first region and the body region, having an impurity concentration of the first conductivity type that is higher than an impurity concentration of the first conductivity type in the first region; and

a third region of the drift region between the second region and the body region, having an impurity concentration of the first conductivity type that is lower than the impurity concentration of the first conductivity type in the second region.

2. The semiconductor device according to claim 1, wherein the impurity concentration of the first conductivity type in the second region is higher than or equal to 1.5 times the impurity concentration of the first conductivity type in the first region.

3. The semiconductor device according to claim 1, wherein the second region is between the first field plate and the second field plate.

4. The semiconductor device according to claim 1, wherein a position at which the impurity concentration of the first conductivity type in the second region is at a maximum that is between two surfaces which are obtained by equally dividing a region between a surface parallel with the second surface and including an end portion on the second surface side of the first field plate, and a surface parallel with the second surface and including a boundary between the drift region and body region, into three regions.

5. The semiconductor device according to claim 1, further comprising:

a first insulating film between the first gate electrode and the first field plate electrode; and

a second insulating film between the second gate electrode and the second field plate electrode.

6. The semiconductor device according to claim 1, wherein the impurity concentration of the first conductivity type in the first region is substantially the same as the impurity concentration of the first conductivity type in the third region.

7. The semiconductor device according to claim 1, further comprising:

a source electrode on the first surface and is electrically coupled to the source region; and

a drain electrode on the second surface and is electrically coupled to the drift region.

8. The semiconductor device according to claim 1, wherein the semiconductor layer is silicon.

9. The semiconductor device according to claim 7, further comprising a drain region of the first conductivity type between the drift region and the drain electrode.

10. A semiconductor device, comprising:

a semiconductor layer having a first surface and a second surface;

a drift region of a first conductivity type in the semiconductor layer;

a body region of a second conductivity type in the semiconductor layer between the drift region and the first surface;

a source region of the first conductivity type in the semiconductor layer between the body region and the first surface;

a first gate electrode;

a second gate electrode, the body region being between the first gate electrode and the second gate electrode;

a first gate insulating film between the first gate electrode and the body region;

a second gate insulating film between the second gate electrode and the body region;

a first field plate electrode between the second surface and the first gate electrode;

a second field plate electrode between the second surface and the second gate electrode;

a first field plate insulating film between the first field plate electrode and the drift region;

a second field plate insulating film between the second field plate electrode and the drift region;

a first region of the drift region having at least a portion between the first field plate electrode and the second field plate electrode;

a second region of the drift region between the first region and the body region, and having an impurity concentration of the first conductivity type that is higher than an impurity concentration of the first conductivity type in the first region;

a third region of the drift region between the second region and the body region, and having an impurity concentration of the first conductivity type that is lower than the impurity concentration of the first conductivity type in the second region;

a source electrode on the first surface and electrically coupled to the source region;

a drain electrode on the second surface and electrically coupled to the drift region; and

a drain region of the first conductivity type between the drift region and the drain electrode.

11. The semiconductor device according to claim 10, wherein the impurity concentration of the first conductivity type in the second region is higher than or equal to 1.5 times the impurity concentration of the first conductivity type in the first region.

12. The semiconductor device according to claim 11, wherein the second region is between the first field plate and the second field plate.

13. The semiconductor device according to claim 10, wherein a position in which the impurity concentration of the first conductivity type of the second region is the maximum is placed between two surfaces which are obtained by equally dividing a region between a surface parallel with the second surface and including an end portion on the second surface side of the first field plate, and a surface parallel with the second surface and including a boundary between the drift region and body region, into three regions.

14. The semiconductor device according to claim 13, further comprising:

a first insulating film between the first gate electrode and the first field plate electrode; and

a second insulating film between the second gate electrode and the second field plate electrode.

15. The semiconductor device according to claim 10, wherein the impurity concentration of the first conductivity type in the first region is substantially the same as the impurity concentration of the first conductivity type in the third region.

16. The semiconductor device according to claim 15, wherein the semiconductor layer is single crystal silicon.

17. The semiconductor device according to claim 10, wherein the first gate electrode and the first field plate electrode are in a trench in the semiconductor layer.

18. A semiconductor device, comprising:

a single crystal semiconductor layer that has a first surface and a second surface;

a drift region of a first conductivity type in the semiconductor layer;

a body region of a second conductivity type in the semiconductor layer between the drift region and the first surface;

a source region of the first conductivity type in the semiconductor layer between the body region and the first surface;

a first gate electrode;

a second gate electrode, the body region being between the first gate electrode and the second gate electrode;

a first gate insulating film between the first gate electrode and the body region;

a second gate insulating film between the second gate electrode and the body region;

a first field plate electrode between the second surface and the first gate electrode;

a second field plate electrode between the second surface and the second gate electrode;

a first field plate insulating film between the first field plate electrode and the drift region;

a second field plate insulating film between the second field plate electrode and the drift region;

a first region in the drift region having at least a portion between the first field plate electrode and the second field plate electrode;

a second region in the drift region between the first region and the body region, and having an impurity concentration of the first conductivity type that is higher than an impurity concentration of the first conductivity type in the first region;

a third region in the drift region between the second region and the body region, and having an impurity concentration of the first conductivity type that is lower than the impurity concentration of the first conductivity type in the second region;

a source electrode on the first surface and electrically coupled to the source region;

a drain electrode on the second surface and electrically coupled to the drift region; and

a drain region of the first conductivity type between the drift region and the drain electrode.

19. The semiconductor device according to claim 18, wherein the impurity concentration of the first conductivity type in the second region is higher than or equal to 1.5 times the impurity concentration of the first conductivity type in the first region.

20. The semiconductor device according to claim 18, wherein a position in which the impurity concentration of the first conductivity type of the second region is the maximum is placed between two surfaces which are obtained by equally dividing a region between a surface parallel with the second surface and including an end portion on the second surface side of the first field plate, and a surface parallel with the second surface and including a boundary between the drift region and body region, into three regions.