Semiconductor device and method of manufacturing the same

A semiconductor device comprising:

• a first conductivity-type drift layer;
• a second conductivity-type base layer on a front side of the drift layer;
• a plurality of trench gate structures, each trench gate structure including a trench reaching the drift layer by penetrating the base layer, a gate insulation layer on a wall surface of the trench, and a gate electrode on the gate insulation layer, the trench gate structure having a length direction parallel to a planar direction of the drift layer, a width direction parallel to the planar direction of the drift layer and perpendicular to the length direction, and a depth direction perpendicular to the planar direction of the drift layer;
• a first conductivity-type emitter layer located in a surface portion of the base layer and located adjacent to the trench gate structure;
• and
• a second conductivity-type collector layer located across the drift layer from the emitter layer, wherein
• the trench gate structure has a bottom portion and an opening portion, the bottom portion defining a bottom of the trench gate structure, the opening portion located on an opposite side of the trench gate structure from the bottom portion in the depth direction,
• the bottom portion of the trench gate structure is located in the drift layer and expands in the width direction so that a distance between the bottom portions of adjacent trench gate structures is less than a distance between the opening portions of adjacent trench gate structures in the width direction, and
• a thickness of the gate insulation layer on the wall surface of the trench of the bottom portion is greater than a thickness of the gate insulation layer on the wall surface of the trench of the opening portion.