Semiconductor device and method of manufacturing the same

A semiconductor device comprising:

• a semiconductor substrate having a main surface and a back surface opposite to the main surface;
• a drift region of a first conductivity type disposed in the semiconductor substrate;
• a base region of a second conductivity type disposed in the semiconductor substrate on a side of the main surface relative to the drift region;
• a source region of the first conductivity type disposed in the semiconductor substrate on the side of the main surface relative to the drift region such that the base region lies between the source region and the drift region;
• and
• a gate electrode disposed in the base region lying between the source region and the drift region, with the gate electrode being insulated from the base region,
• the semiconductor substrate having a trench in the main surface,
• the gate electrode being formed in the trench,
• a distribution of an impurity concentration in the base region having a plurality of peak values along a direction of a depth from the main surface toward the back surface, and
• the number of peak values being four or more, wherein
• the semiconductor device further comprises a column region of the second conductivity type extending from the base region toward the back surface in the semiconductor substrate,
• an impurity concentration in the column region is higher than any of the plurality of peak values in the distribution of the impurity concentration in the base region, and
• the plurality of peak values in the distribution of the impurity concentration in the base region are closer to the impurity concentration in the column region as a distance from the main surface is greater.