Patent ID: 7786532

Claim:
A semiconductor device comprising: a first semiconductor substrate of a first conductivity type; a first semiconductor region of a second 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 in contact with said first semiconductor substrate, to a depth greater than a depth of said first semiconductor region and surrounding said first semiconductor region and 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 said second semiconductor region; and a third electrode electrically coupled to said first semiconductor substrate through a second main surface of said first semiconductor substrate, a distance, t, from a junction interface between said third semiconductor region just below said first semiconductor region and said first semiconductor substrate to the second main surface of said first semiconductor substrate and a distance, L, between the first and second semiconductor regions satisfying a relation of L≦t≦2×L.