Patent ID: 7473965

Claim:
A semiconductor device comprising: a semiconductor substrate of a first conductivity type; a first semiconductor region of the first conductivity type formed above a first main surface of said first semiconductor substrate; a second semiconductor region of the first conductivity type formed at a distance from said first semiconductor region above the first main surface of said first semiconductor substrate; a third semiconductor region of a second conductivity type formed at least on a region between said first semiconductor region and said second semiconductor region above the first main surface side of said first semiconductor substrate; a fourth semiconductor region of a second conductivity type formed in said second semiconductor region and on the surface of said second semiconductor region; a fifth semiconductor region of the second conductivity type formed in contact with said first semiconductor substrate, to a depth deeper than depths of the first, second and third semiconductor regions and surrounding the second and third semiconductor regions and being formed in contact with at least a part of said second semiconductor region and encompassing said second semiconductor region; a first electrode electrically connected to said first semiconductor region; a second electrode electrically connected to the second and fourth semiconductor regions; a conductive layer formed on said second semiconductor region between said fourth semiconductor region and said fifth semiconductor region with an insulating film interposed between the second semiconductor region and the conductive layer; and a fourth electrode electrically coupled to said first semiconductor substrate, a distance, t, from a junction interface between said fifth semiconductor region just below said third semiconductor region and said first semiconductor substrate to a second main surface of said first semiconductor substrate and a distance, L, between the second and third semiconductor regions satisfying a relation of L≦t≦2×L.