Silicon carbide semiconductor device

• US 9,679,986 B2
• Filed: 12/02/2015
• Issued: 06/13/2017
• Est. Priority Date: 09/12/2012
• Status: Active Grant

• Current Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Masuda, Takeyoshi, Saitoh, Yu, Hiyoshi, Toru, Wada, Keiji, Hayashi, Hideki
• Primary Examiner(s): Wilczewski, Mary
• Assistant Examiner(s): Peterson, Erik T
• Application Number:
  US14/957,267
• Publication Number:
  US 20160087065A1
• Time in Patent Office: 559 Days
• Field of Search: None
• 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 method for manufacturing a silicon carbide semiconductor device comprising the steps of:

preparing a silicon carbide substrate having a silicon carbide layer;

forming a trench at said silicon carbide layer;

forming a bottom insulating film at a bottom portion of said trench;

forming a trench insulating film under said bottom insulating film to cover said bottom portion and a side wall of said trench after forming said bottom insulating film;

forming a gate electrode on said bottom insulating film on said trench insulating film, and

wherein said trench insulating film is formed by thermally oxidizing said silicon carbide layer after forming said bottom insulating film.

2. The method for manufacturing a silicon carbide semiconductor device according to claim 1, said silicon carbide layer having a first conductivity type and further comprising a step of:

forming an impurity region of a second conductivity type at said silicon carbide layer before forming said trench, wherein

said trench is formed to penetrate said impurity region.

3. The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein

said trench insulating film is formed at a first temperature higher than a second temperature at which said bottom insulating film is formed.

4. The method for manufacturing a silicon carbide semiconductor device according to claim 3, wherein

said first temperature is 1300°

C. or more and said second temperature is not less than 800°

C. and not more than 950°

C.

5. The method for manufacturing a silicon carbide semiconductor device according to claim 1, further comprising a step of:

forming a silicon film on said bottom portion of said trench before forming said bottom insulating film, wherein

said bottom insulating film is formed by thermally oxidizing said silicon film.