Patent ID: 7462530

Claim:
A method for manufacturing a semiconductor device, comprising the steps of: forming a buried diffusion layer of a second conductivity type in the surface layer of a prescribed area of a substrate of a first conductivity type; forming a first high-concentration isolation diffusion layer of the first conductivity type in the substrate so as to surround the buried diffusion layer; forming an epitaxial layer of the second conductivity type on the substrate, the buried diffusion layer, and the first high-concentration isolation diffusion layer; forming a low-concentration isolation diffusion layer of the first conductivity type in the epitaxial layer on the first high-concentration isolation diffusion layer, the low-concentration isolation diffusion layer isolating the epitaxial layer into a plurality of island regions; forming a second high-concentration isolation diffusion layer of the first conductivity type in the junction area between the first high-concentration isolation diffusion layer and the low-concentration isolation diffusion layer; forming a high-concentration diffusion layer of the first conductivity type in direct physical contact with an upper layer of said buried diffusion layer; forming, after formation of the epitaxial layer, a first diffusion layer of the first conductivity type in a third island region of the epitaxial layer on the buried diffusion layer; forming a second diffusion layer of the second conductivity type in the third island region adjacent to the first diffusion layer; and forming a high-concentration diffusion layer of the first conductivity type in the junction area between the buried diffusion layer and the first diffusion layer; wherein said step of forming the first diffusion layer is simultaneously performed with said step of forming the low-concentration isolation diffusion layer, and said step of forming the high-concentration diffusion layer is simultaneously performed with said step of forming the second high-concentration isolation diffusion layer.