Characteristics of a semiconductor device are improved. A semiconductor device of the present invention includes: (a) a MISFET arranged in an active region formed of a semiconductor region surrounded by an element isolation region; and (b) an insulating layer arranged below the active region. Further, the semiconductor device includes: (c) a p-type semiconductor region arranged below the active region so as to interpose the insulating layer; and (d) an n-type semiconductor region whose conductivity type is opposite to the p-type, arranged below the p-type semiconductor region. And, the p-type semiconductor region includes a connection region extending from below the insulating layer, and the p-type semiconductor region and a gate electrode of the MISFET are connected to each other by a shared plug which is an integrally-formed conductive film extending from above the gate electrode to above the connection region.