Patent ID: 7078767

Claim:
A semiconductor device comprising: a substrate at least having an insulative surface; a semiconductor film provided on said surface of said substrate comprising a first semiconductor layer of a first conductivity type, a second semiconductor layer of said first conductivity type having an impurity concentration lower than that of said first semiconductor layer, a third semiconductor layer of a second conductivity type opposite to said first conductivity type and a fourth semiconductor layer of said second conductivity type having an impurity concentration lower than that of said third semiconductor layer; and an insulative isolator formed on a surface of said semiconductor film on the far side from said substrate, separately from said surface of said substrate, wherein said second and fourth semiconductor layers form a pn junction extending in the thickness direction of said semiconductor film, said pn junction has a portion separated from said isolator, and a maximum value of a distance parallel to said surface of said substrate between said pn junction and an end of the isolator is not more than 2 μm, when a direction from said end of the isolator toward the isolator in parallel to said surface of said substrate is taken as a positive direction.