Semiconductor device

A semiconductor device comprising:

• a semiconductor substrate of a first conductivity type;
• a first semiconductor layer of the first conductivity type, provided on a front surface of the semiconductor substrate, and having an impurity concentration lower than an impurity concentration of the semiconductor substrate, the first semiconductor layer having a first surface and a second surface that is opposite to the first side and faces the front surface of the semiconductor substrate;
• a second semiconductor layer of a second conductivity type, provided on the first surface of the first semiconductor layer;
• a first semiconductor region of the first conductivity type, selectively provided in a surface layer of the second semiconductor layer;
• a plurality of trenches penetrating the first semiconductor region and the second semiconductor layer, and reaching the first semiconductor layer;
• a plurality of gate electrodes each provided in a corresponding trench of the plurality of trenches, via a gate insulating film;
• a first base region of the second conductivity type, provided in the first semiconductor layer, between adjacent trenches of the plurality of trenches, the first base region being in contact with the second semiconductor layer;
• a plurality of second base regions of the second conductivity type, provided in the first semiconductor layer, second base regions of the plurality of second base regions facing trenches of the plurality of trenches, respectively, in a depth direction;
• a first electrode in contact with the first semiconductor region and the second semiconductor layer;
• and
• a second electrode provided on a back surface of the semiconductor substrate, wherein
• each of the plurality of second base regions has a first surface facing the second electrode and a second surface facing the first electrode, and a curvature of the first surface is smaller than a curvature of the second surface.