Patent ID: 8716142

Claim:
A method of manufacturing a semiconductor device, comprising: preparing a semiconductor substrate of a first conductivity type; removing a portion from a surface of the semiconductor substrate to form a concave surface region; forming trenches having a side surface and a bottom surface in a region to become a channel, such that the semiconductor substrate surface has a planar portion and trench portions, wherein the trenches are spaced away from the concave surface region along the surface by a constant distance, such that the concave surface region follows a contour of the side surface of the trenches; forming a gate insulating film on the side surface and the bottom surface of the trenches and on the surface of the planar portion; forming a gate electrode on the gate insulating film, such that the gate electrode extends farther in a channel length direction in the trench portions than in the planar portion; and forming a source region of a second conductivity type and a drain region of the second conductivity type in the substrate below the concave surface region, such that the source and drain regions are adjacent to the side surfaces of the trenches and sandwich the gate electrode therebetween below the concave surface region.