Semiconductor device and method of manufacturing semiconductor device

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

• providing a semiconductor substrate of a first conductivity type, the semiconductor substrate having a front surface and a back surface opposite to each other;
• forming, on the front surface of the semiconductor substrate, a first semiconductor layer of the first conductivity type, the first semiconductor layer having an impurity concentration lower than that of the semiconductor substrate and having a first side facing the semiconductor substrate and a second side opposite to the first side;
• selectively forming, in the first semiconductor layer, a first semiconductor region of the first conductivity type, the first semiconductor region having a peak impurity concentration higher than that of the first semiconductor layer;
• selectively forming, in the first semiconductor layer, a first base region of a second conductivity type;
• forming, on a surface of the first semiconductor layer at the second side thereof, a second semiconductor layer of the second conductivity type;
• selectively forming, in the second semiconductor layer at a surface thereof, a second semiconductor region of the first conductivity type;
• forming a trench that penetrates the second semiconductor layer and the second semiconductor region, and reaches the first semiconductor layer;
• forming, in the trench, a gate electrode via a gate insulating film;
• forming an interlayer insulating film on the gate electrode;
• forming a first electrode in contact with the second semiconductor layer and the second semiconductor region;
• and
• forming a second electrode on the back surface of the semiconductor substrate, wherein
• forming a trench includes forming a plurality of trench portions, each of which extends in a first direction,
• forming the first semiconductor region includes forming a plurality of first semiconductor region portions, each between adjacent two of the trench portions, the first semiconductor region being closer to the second electrode than is the first base region, and
• forming the first base region includes forming the first base region along a second direction intersecting the first direction, at a depth that is the same as a bottom of the trench, or is closer to the second electrode than is the bottom of the trench.