Semiconductor device, method for manufacturing same, power conversion device, three-phase motor system, automobile, and railway carriage

A semiconductor device, comprising:

• a first conductive type semiconductor substrate;
• a drain electrode formed on a back side of the semiconductor substrate;
• a drift layer of the first conductive type formed on the semiconductor substrate;
• a source area of the first conductive type;
• a current-diffused area of the first conductive type electrically connected to the drift layer;
• a body layer of a second conductive type reverse to the first conductive type in contact with the source area and the current diffused layer;
• a trench which pierces the source area, the body layer and the current diffused layer, which is shallower than the body layer, and the bottom of which is in contact with the body layer;
• a gate insulating film formed on an inner wall of the trench;
• a gate electrode formed on the gate insulating film;
• and
• a gate insulating film protective layer formed between the current-diffused layer and the gate electrode.

A manufacturing method of a semiconductor device, comprising the steps of:

• preparing a silicon carbide semiconductor substrate of a first conductive type on which an epitaxial layer of the first conductive type is formed;
• forming a first area of a second conductive type reverse to the first conductive type in the epitaxial layer;
• forming a second area of the first conductive type in the first area;
• forming a third area of the second conductive type in the second area;
• forming a trench shallower than the first area and deeper than the third area;
• forming an insulating film on an inner wall of the trench;
• and
• forming a gate electrode on the insulating film.