Patent ID: 7932580

Claim:
A semiconductor device comprising: a one-conductivity-type semiconductor substrate; an opposite-conductivity-type epitaxial layer formed on the semiconductor substrate; and a one-conductivity-type isolation region which divides the epitaxial layer into a plurality of element formation regions, wherein: the isolation region is formed by connecting a first one-conductivity-type buried diffusion layer formed across the semiconductor substrate and the epitaxial layer, a second one-conductivity-type buried diffusion layer formed in the epitaxial layer and a first one-conductivity-type diffusion layer formed in the epitaxial layer with each other, the first one-conductivity-type buried diffusion layer and the first one-conductivity-type diffusion layer partially overlap with each other in the epitaxial layer, an impurity concentration peak of the first one-conductivity-type buried diffusion layer is positioned closer to the substrate than a center of the epitaxial layer, and an impurity concentration peak of the second one-conductivity-type buried diffusion layer and an impurity concentration peak of the first one-conductivity-type diffusion layer are positioned closer to the surface of the epitaxial layer than the center of the epitaxial layer.