Silicon carbide semiconductor device and method for manufacturing same

A method of manufacturing a silicon carbide semiconductor device, comprising:

• preparing a semiconductor substrate, which is made of silicon carbide having a first conductivity type, and includes a high-concentration impurity layer on a rear surface side and a drift layer arranged on a front surface side and having an impurity concentration lower than the high-concentration impurity layer;
• forming a base region made of silicon carbide on the drift layer;
• forming a source region, which is made of silicon carbide having the first conductivity type with an impurity concentration higher than the drift layer, in an upper portion of the base region;
• forming a trench extending from a surface of the source region to a position deeper than the base region;
• providing a trench gate structure by forming a gate insulating film on an inner wall of the trench, and forming a gate electrode on the gate insulating film;
• forming a source electrode electrically connected to the source region;
• and
• forming a drain electrode electrically connected to the high-concentration impurity layer on the rear surface side of the semiconductor substrate, wherein:
• in the forming of the base region, a high-concentration base region and a low-concentration base region having a second conductivity type with an impurity concentration lower than the high-concentration base region are stacked each other;
• and
• in the forming of the trench, the trench is formed to be deeper than the base region, and each of the high-concentration base region and the low-concentration base region contacts a side surface of the trench.