A dielectric isolation type semiconductor device includes a dielectric isolation type substrate in which a support substrate, an embedded dielectric layer, and a first conductive type semiconductor substrate of a low impurity concentration are laminated one over another. The semiconductor substrate includes a first semiconductor region of a first conductive type having a high impurity concentration, a second semiconductor region of a second conductive type having a high impurity concentration arranged so as to surround the first semiconductor region, a first main electrode joined to a surface of the first semiconductor region, and a second main electrode joined to a surface of the second semiconductor region. A first dielectric portion is arranged adjacent the embedded dielectric layer so as to surround a region of the support substrate superposed on the first semiconductor region in a direction of lamination thereof, and a wire connected with the first main electrode.