Patent ID: 8004040

Claim:
A semiconductor device comprising: a well area of a second conductivity type formed on a semiconductor substrate of a first conductivity type, the second conductivity type being different from the first conductivity type; a body area of the first conductivity type formed within the well area; a source area of the second conductivity type formed within the body area; a drain area of the second conductivity type formed at a distance from the body area within the well area, the drain area having a higher concentration than the well area; a gate insulating film formed so as to overlay a part of the body area; a gate electrode formed on the gate insulating film; and a buried diffusion area of the first conductivity type which makes contact with a bottom of the body area and extends to an area beneath the drain area in a direction parallel to a surface of the semiconductor substrate within the well area, wherein the buried diffusion area is not formed beneath a part of the drain area which is a potential setting area, but formed beneath the other part of the drain area except the potential setting area and completely overlaps to the drain area except the potential setting area in the vertical direction to the substrate, so that an electric contact is made between the potential setting area and the well area below the buried diffusion area.