Patent ID: 8466515

Claim:
A semiconductor device comprising: a semiconductor substrate having a main surface; a dielectric portion formed to contact the main surface of said semiconductor substrate and having a first thickness and a second thickness larger than said first thickness; a semiconductor region of a first conductivity type formed to contact said dielectric portion and having a first impurity concentration; a first impurity region of the first conductivity type formed from a surface of said semiconductor region to a first depth in a first region of said semiconductor region, said first region being located directly above a portion which is a part of said dielectric portion and has said first thickness; a second impurity region of a second conductivity type formed from the surface of said semiconductor region to a second depth larger than said first depth in said first region to surround said first impurity region laterally and from below; a gate electrode portion formed on a surface of a portion of said second impurity region located between said first impurity region and said semiconductor region, with a gate insulating film interposed between said gate electrode portion and the surface of the portion of said second impurity region; a third impurity region of the second conductivity type having a second impurity concentration and formed from the surface of said semiconductor region to a third depth in a second region of said semiconductor region, said second region being located at a distance from said second impurity region and directly above a portion which is a part of said dielectric portion and has said second thickness; and a depletion layer block portion including a conductive region and formed at a predetermined position in said second region to extend from the surface of said semiconductor region and reach said dielectric portion wherein the depletion layer block portion is formed directly on and directly contacts the upper surface of the portion which is the part of said dielectric portion.