A semiconductor device is provide that includes: a semiconductor body having a first surface, an inner region, and an edge region; a pn junction between a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type, the pn-junction extending in a lateral direction of the semiconductor body in the inner region; a recess extending from the first surface in the edge region into the semiconductor body, the recess comprising at least one sidewall; a dielectric filling the recess. In the dielectric, a dielectric number, in the lateral direction, decreases as a distance from the first sidewall increases.

A thyristor semiconductor includes a first layer, located on a first surface of a substrate, where the first layer is a first P layer. A second layer, located on a second surface of the substrate, is a second P layer. The second surface is opposite the first surface. A third layer is located between the first layer and the substrate. An isolation region is located along an edge of the substrate The isolation region is adjacent the second P layer. An emitter, next to the third layer, is connected to a cathode.