Silicon carbide semiconductor device and method of manufacturing silicon carbide semiconductor device

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

• preparing a silicon carbide semiconductor substrate of a first conductivity type, having a first main surface and a second main surface opposite to each other;
• forming a first semiconductor layer of the first conductivity type at the first main surface of the silicon carbide semiconductor substrate, the first semiconductor layer having an impurity concentration that is lower than an impurity concentration of the silicon carbide semiconductor substrate, the first semiconductor layer having a first surface and a second surface opposite to each other, the second surface facing the silicon carbide semiconductor substrate;
• forming a second semiconductor layer of a second conductivity type at the first surface of the first semiconductor layer, the second semiconductor layer having a first surface and a second surface opposite to each other, the second surface facing the first semiconductor layer;
• forming a plurality of first high-concentration regions of the second conductivity type in the first semiconductor layer;
• selectively forming a plurality of second high-concentration regions of the second conductivity type in the first semiconductor layer and the second semiconductor layer, each of the plurality of second high-concentration regions having
• an upper surface exposed from the first surface of the second semiconductor layer, and
• a lower surface partially in contact with upper surfaces of the plurality of first high-concentration regions;
• selectively forming a plurality of first semiconductor regions of the first conductivity type in the second semiconductor layer at the first surface thereof;
• forming a plurality of trenches penetrating through respective ones of the plurality of first semiconductor regions and the second semiconductor layer and reaching the first semiconductor layer;
• forming a plurality of gate electrodes, each gate electrode being embedded in a corresponding one of the plurality of trenches, via a gate insulating film;
• forming a first electrode at surfaces of the plurality of second high-concentration regions and the plurality of first semiconductor regions;
• and
• forming a second electrode at the second main surface of the silicon carbide semiconductor substrate, wherein
• each of the plurality of first high-concentration regions faces a corresponding one of the plurality of trenches in a depth direction of the silicon carbide semiconductor device, and
• each of the plurality of second high-concentration regions is in contact with a corresponding one of the plurality of first semiconductor regions and is formed periodically in a longitudinal direction of the plurality of trenches between a corresponding adjacent two of the plurality of trenches.