Patent ID: 8168494

Claim:
A method of manufacturing a semiconductor device, comprising: a well forming step of forming a well of a first conductivity type on a semiconductor substrate; a second well forming step of forming two wells, including a second well, of a second conductivity type in the well of the first conductivity type, wherein the second well forming step comprises forming the second well with a depth that extends into the well of the first conductivity type to a depth of a bottom surface of a gate electrode formed in a concave portion between the two wells of the second conductivity type; a concave portion forming step of forming the concave portion between the two wells of the second conductivity type, with varying depth in a gate width direction; a gate electrode forming step of forming, after forming an insulating film on the concave portion, the gate electrode on an upper surface and inside of the concave portion via the insulating film, wherein the gate electrode is formed with a length of a portion of the gate electrode on the upper surface of the concave portion that is shorter than a length of the gate electrode inside of the concave portion; and a source and drain forming step of implanting ions into the two wells of the second conductivity type to form a source region and a drain region, wherein the implanting of the ions covers a whole upper surface of each of the two wells, and wherein a depth of the implanted ions is uniform and shallower than a bottom of the concave portion.