Semiconductor device and method of manufacturing semiconductor device

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

• providing a base region of a second conductivity type in a surface layer of a drift layer of a first conductivity type;
• providing a plurality of source regions of the first conductivity in a surface layer of the base region;
• providing at least one trench that extends from an upper surface of the drift layer through the base region to an inside of the drift layer;
• providing a protective layer of the second conductivity type in the drift layer located under the trench;
• defining regions partitioned in the trench in plan view as a first region and a second region;
• etching an upper corner portion of the trench in the first region and the second region,
• etching the upper corner portion of the trench in the second region;
• providing a gate insulating film along an inside of the trench including the upper corner portion of the trench;
• providing a gate electrode in the trench surrounded by the gate insulating film;
• providing a source electrode that is electrically connected to the source regions located adjacent to the trench in the first region;
• and
• providing a gate line on an upper surface of the gate electrode provided in the trench in the second region,
• wherein the gate insulating film provided on the upper corner portion of the trench in the second region has a greater radius of curvature than the gate insulating film provided on the upper corner portion of the trench in the first region.