Patent ID: 7002210

Claim:
A semiconductor device comprising: a first impurity region of a first conductivity type formed on a main surface of a semiconductor substrate; a first isolating insulation film formed on a surface of said first impurity region; a second impurity region of a second conductivity type formed at that portion of said first impurity region which is positioned immediately below said first isolating insulation film; a third impurity region of the second conductivity type formed at a surface of a portion of said first impurity region, spaced apart from said first isolating insulation film; a fourth impurity region of the second conductivity type formed on a portion of said first impurity region on a side opposite to said third impurity region with said first isolating insulation film positioned therebetween, spaced apart from said first isolating insulation film; a first electrode portion formed on that portion of said first impurity region which is sandwiched between said second impurity region and said third impurity region; a second electrode portion formed on that portion of said first impurity region which is sandwiched between said second impurity region and said fourth impurity region; a second isolating insulation film formed spaced apart from said first isolating insulation film, at a surface of that portion of said first impurity region which is on a side where said third impurity region is positioned, with respect to said first isolating insulation film; and a third isolating insulation film formed spaced apart from said first isolating insulation film, at a surface of that portion of said first impurity region which is on a side where said fourth impurity region is positioned, with respect to said first isolating insulation film; wherein said third impurity region includes a first concentration region having a prescribed impurity concentration formed at that portion of said first impurity region which is positioned immediately below said second isolating insulation film, and a second concentration region having an impurity concentration higher than said first concentration region, electrically connected to said first concentration region and formed in a direction away from said first isolating insulation film with respect to said second isolating insulation film; and said fourth impurity region includes a third concentration region having a prescribed concentration formed at that portion of said first impurity region which is positioned immediately below said third isolating insulation film, and a fourth concentration region having an impurity concentration higher than said third concentration region, electrically connected to said third concentration region and formed in a direction away from said first isolating insulation film with respect to said third isolating insulation film.