Patent ID: 8487408

Claim:
A semiconductor device comprising: a semiconductor layer; a first-conductivity-type deep well formed in the semiconductor layer; a first second-conductivity-type impurity layer formed in a part of the surface layer of the deep well; a first first-conductivity-type impurity layer formed in a part of the surface layer of the first second-conductivity-type impurity layer; a second first-conductivity-type impurity layer provided at a position, brought into contact with the deep well, of the semiconductor layer; a second second-conductivity-type impurity layer formed in the surface layer of the deep well, positioned between the first second-conductivity-type impurity layer and the second first-conductivity-type impurity layer in a plan view, connected to the first second-conductivity-type impurity layer, having an impurity concentration larger than that of the first second-conductivity-type impurity layer, and having a depth shallower than that of the first second-conductivity-type impurity layer; a first-conductivity-type buried region formed in the semiconductor layer, having the top surface thereof brought into contact with the deep well and the second first-conductivity-type impurity layer, and having an impurity concentration larger than that of the deep well; and a third second-conductivity-type impurity layer formed in the surface layer of the first second-conductivity-type impurity layer, brought into contact with the first first-conductivity-type impurity layer, and having an impurity concentration larger than that of the second second-conductivity-type impurity layer.