SiC semiconductor device and method for manufacturing the same

A method for manufacturing a silicon carbide semiconductor device having a MOS structure, the method comprising:

• preparing a substrate made of silicon carbide and having a principal surface;
• forming a channel region made of silicon carbide on the substrate, wherein the channel region provides a current path as a channel;
• forming a first impurity region on an upstream side of the current path and a second impurity region on a downstream side of the current path;
• forming a gate insulating film on a surface of the channel region;
• forming a gate on the gate insulating film;
• performing a heat treatment, and
• performing at least one of round-off oxidizing, reflowing, and electrode annealing wherein
• the channel of the channel region for flowing current between the first impurity region and the second impurity region is controlled by a voltage applied to the gate,
• an interface between the channel region and the gate insulating film provides a channel surface having a (000-1)-orientation surface,
• the performing the heat treatment includes:
• reducing temperature in a range between 650° C. and 850° C.;
• and
• maintaining a wet atmosphere or a hydrogen atmosphere continuously during reducing the temperature,
• the maintaining the wet atmosphere or the hydrogen atmosphere is performed when the temperature is equal to or greater than 650° C. after the forming the gate insulating film,
• the round-off oxidizing rounds a surface of the gate,
• the reflowing forms an interlayer insulating film, and
• the electrode annealing provides an annealed electrode.