Patent ID: 7772677

Claim:
A semiconductor device comprising: a semiconductor substrate comprising: a first high impurity concentration layer of a first conductivity type; a low impurity concentration drift layer of the first conductivity type; and a second high impurity concentration layer of a second conductivity type, the second high impurity concentration layer and the drift layer forming a p-n main junction therebetween, wherein the drift layer is formed between the first high impurity concentration layer and the second high impurity concentration layer; an active region where current flows in the direction of the thickness of the semiconductor substrate; and a junction termination structure surrounding an outer periphery of the active region, the junction termination structure comprising: a sidewall extending between the first high impurity concentration layer and the second high impurity concentration layer, and forming a positive bevel angle between 30-85° inclusive with respect to a principal surface of the first high impurity concentration layer; and a surface region of the first conductivity type defining an outer periphery of the junction termination structure and extending along the sidewall and extending between the first high impurity concentration layer and the second high impurity concentration layer, wherein the surface region has an outer peripheral surface that is parallel with the sidewall so that substantially the same positive bevel angle is provided with respect to the principal surface of the first high impurity concentration layer, wherein the surface region has an impurity concentration lower than an impurity concentration of the first high impurity concentration layer and an impurity concentration of the second high impurity concentration layer, but higher than an impurity concentration of the drift layer, to decrease electric field strength at an interface between the drift layer and the first high impurity concentration layer so that a depletion layer reaches the first high impurity concentration layer with a voltage lower than the voltage in the active region and to inhibit the depletion layer from spreading in the sidewall, and wherein the impurity concentration in the surface region is within a range between 5×10 11 cm −2 and 5×10 12 cm −2 and increases as the positive bevel angle increases from 30° to 85°.