Patent ID: 7053451

Claim:
A semiconductor device having an SOI structure formed by a semiconductor substrate < 1 >, an embedded insulating layer < 2 > and an SOI layer < 3 >, comprising: a plurality of element forming regions provided in said SOI layer, each formed with a prescribed element; an isolation film < 31 > provided in an upper layer part of said SOI layer for isolating said plurality of element forming regions from each other; a first conductivity type semiconductor region < 11 , 12 > provided under said isolation film as part of said SOI layer, said semiconductor region being formed in contact with at least one of said plurality of element forming regions having a first conductivity type among said plurality of element forming regions; and a first conductivity type body region < 10 > provided in said SOI layer and capable of being externally fixed in electric potential, said body region being in contact with said semiconductor region, wherein said semiconductor region at least partially has a first conductivity type impurity region not mixed with an impurity of a second conductivity type different from said first conductivity type but doped by only an impurity of said first conductivity type.