Semiconductor device and manufacturing method of semiconductor device

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

• forming a trench, in a drift layer of a first conductivity type formed on an upper surface of a drain layer of a first conductivity type, from an upper surface side of the drift layer toward the drain layer of the drift layer;
• forming a first insulating film on an inner wall of the trench;
• forming a field plate electrode inside of the trench via the first insulating film;
• forming a second insulating film on an upper surface of the field plate electrode, the inner wall of the trench, and upper surface of the drift layer;
• forming a conductive film, via the second insulating film, on the inner wall of the trench and on the upper surface of the drift layer, the conductive film comprising a recess in the trench;
• forming a mask in the recess and the upper surface in the periphery of the recess;
• etching the conductive film from the upper surface of the conductive film and from both sides of the mask to form a gate region of a U-shape;
• removing the mask to form the recess on a surface of the gate region;
• forming a base region on an upper surface of the drift layer other than the trench;
• forming a source region on an upper surface of the base region;
• forming a third insulating film on an upper surface of the source region and an upper surface of the gate region to fill the recess;
• and
• forming a gate contact reaching the gate region through the third insulating film.