Patent ID: 7868385

Claim:
A semiconductor device, comprising: a semiconductor substrate of a first conductivity type; a gate insulating film provided on a surface of the semiconductor substrate; a gate electrode provided on the gate insulating film; a first drain region of a second conductivity type corresponding to an opposite conductivity type with respect to the first conductivity type, the first drain region being provided in the vicinity of an end portion of the gate electrode; a drain contact region of the second conductivity type that is provided within the first drain region, the drain contact region having an impurity concentration that is higher than an impurity concentration of the first drain region; and a second drain region of the second conductivity type that is provided around and underneath the drain contact region; wherein the second drain region is arranged to have an impurity concentration that is lower than the impurity concentration of the drain contact region and higher than the impurity concentration of the first drain region, the second drain region has a greater dimension in a gate width direction than a dimension of the first drain region in the gate width direction, an end of the second drain region opposite to the gate electrode being more distant from the gate electrode than an end of the first drain region opposite to the gate electrode, and the second drain region having an impurity region extending to a deeper position than the first drain region in the depth direction of the semiconductor substrate; an end portion of the second drain region at the gate electrode side is positioned away from the end portion of the gate electrode by a distance determined based on possible short channel effect and on-resistance reduction; an end portion of the drain contact region at the gate electrode side is positioned away from the end portion of the second drain region at the gate electrode side by said distance; and said distance is greater than or equal to a depth of a bottom portion of the second drain region.