SILICON CARBIDE SEMICONDUCTOR DEVICE

• US 20140070233A1
• Filed: 08/02/2013
• Published: 03/13/2014
• Est. Priority Date: 09/12/2012
• Status: Abandoned Application

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Masuda, Takeyoshi, Saitoh, Yu, Hayashi, Hideki, Hiyoshi, Toru, Wada, Keiji
• Application Number:
  US13/958,073
• Publication Number:
  US 20140070233A1
• Time in Patent Office: Days
• US Class Current: 257/77
• CPC Class Codes: H01L 21/049 Conductor-insulator-semiconductor electrodes, e.g. MIS contacts
• CPC Class Codes: H01L 29/045 by their particular orientation of crystalline planes
• CPC Class Codes: H01L 29/1608 Silicon carbide
• CPC Class Codes: H01L 29/4236 within a trench, e.g. trench gate electrode, groove gate electrode
• CPC Class Codes: H01L 29/42368 the thickness being non-uniform
• CPC Class Codes: H01L 29/512 the variation being parallel to the channel plane
• CPC Class Codes: H01L 29/513 the variation being perpendicular to the channel plane
• CPC Class Codes: H01L 29/517 the insulating material comprising a metallic compound, e.g. metal oxide, metal silicate H01L29/518 takes precedence
• CPC Class Codes: H01L 29/66068 the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
• CPC Class Codes: H01L 29/78 with field effect produced by an insulated gate H01L29/7725, H01L29/775, H01L29/778 take precedence
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236

Abstract

A gate insulating film is provided on a trench. The gate insulating film has a trench insulating film and a bottom insulating film. The trench insulating film covers each of a side wall and a bottom portion. The bottom insulating film is provided on the bottom portion with a trench insulating film being interposed therebetween. The bottom insulating film has a carbon atom concentration lower than that of the trench insulating film. The gate electrode is in contact with a portion of the trench insulating film on the side wall. Accordingly, a low threshold voltage and a large breakdown voltage can be attained.

Claims

1. A silicon carbide semiconductor device comprising:

a silicon carbide substrate including a first layer having first conductivity type, a second layer provided on said first layer and having second conductivity type, and a third layer provided on said second layer, separated from said first layer by said second layer, and having said first conductivity type, said silicon carbide substrate being provided with a trench having a side wall and a bottom portion, said side wall extending through said third layer and said second layer and reaching said first layer, said bottom portion being formed of said first layer;

a gate insulating film provided on said trench, said gate insulating film including a trench insulating film and a bottom insulating film, said trench insulating film covering each of said side wall and said bottom portion, said bottom insulating film being provided on said bottom portion with said trench insulating film being interposed therebetween, said bottom insulating film having a carbon atom concentration lower than that of said trench insulating film; and

a gate electrode provided in said trench, said gate electrode being in contact with a portion of said trench insulating film on said side wall.

2. The silicon carbide semiconductor device according to claim 1, wherein a total of a thickness of said trench insulating film on said bottom portion and a thickness of said bottom insulating film is larger than a thickness of said trench insulating film on said side wall.

3. The silicon carbide semiconductor device according to claim 1, wherein on said bottom portion, a thickness of said bottom insulating film is larger than that of said trench insulating film.

4. The silicon carbide semiconductor device according to claim 1, wherein a thickness of said trench insulating film on said bottom portion is smaller than a thickness of said trench insulating film on said side wall.

5. The silicon carbide semiconductor device according to claim 1, wherein the carbon atom concentration of said trench insulating film is more than 1×

10¹⁵ cm<sup>−

3</sup>, and the carbon atom concentration of said bottom insulating film is less than 1×

10¹⁵ cm<sup>−

3</sup>.

6. The silicon carbide semiconductor device according to claim 1, wherein said bottom insulating film has a thickness of more than 100 nm.

7. The silicon carbide semiconductor device according to claim 1, wherein said trench insulating film is a thermal oxidation film of silicon carbide.

8. The silicon carbide semiconductor device according to claim 1, wherein said bottom insulating film is formed of at least any one of silicon oxide, silicon nitride, and phosphorus silicate glass.

9. The silicon carbide semiconductor device according to claim 1, wherein said bottom insulating film is a thermal oxidation film of a film containing silicon and containing no carbon.