Method of manufacturing semiconductor device

A method of manufacturing a semiconductor device demarcated into an active region, a boundary region surrounding the active region, and an edge region surrounding the boundary region in plan view, the method comprising:

• a step (a) of forming a first mask on a first main surface of the semiconductor substrate having a drift layer of a first conductivity type;
• a step (b) of forming a base layer of a second conductivity type on a side of the first main surface of at least a part a region of the drift layer in the active region by implanting impurity ions of the second conductivity type into the first main surface of the semiconductor substrate using the first mask;
• a step of (c) of forming an impurity layer of the first conductivity type on the side of the first main surface of the base layer by implanting impurity ions of the first conductivity type into the first main surface of the semiconductor substrate using the first mask;
• a step (d) of forming trenches reaching the drift layer from the first main surface of the semiconductor substrate after the steps (b) and (c);
• a step (e) of embedding a gate electrode inside the trenches via a gate insulating film;
• a step (f) of forming a second mask having a different pattern from that of the first mask on the first main surface of the semiconductor substrate;
• and
• a step (g) of converting a part of the impurity layer into a first contact layer of the second conductivity type by implanting impurity ions of the second conductivity type having a dosage higher than that of the impurity ions of the first conductivity type implanted at the step (c) into the first main surface of the semiconductor substrate using the second mask.