| 摘要 |
PURPOSE:To improve a semiconductor device in a breakdown strength by a method wherein a second conductivity type layer low in impurity concentration is provided in contact with a second conductivity type region side of a first conductivity type layer high in impurity concentration. CONSTITUTION:A P<+> layer 7, whose impurity concentration is nearly equal to that of an N<+> layer 2, is provided surrounding the N<+> layer 2 contacted with a cathode 4. An N layer 8, whose impurity concentration is as low as that of a P-type substrate 1, is added inside the region surrounding the P<+> layer 7. Therefore, even if a potential of an inversion layer 6 generated under an SiO2 film 3 grows equal to that of the cathode electrode 4 through the intermediary of the N<+> layer 2, a reverse bias between the potential of the inversion layer 6 and a potential of an anode electrode 9 applied onto the P-type substrate 1 is borne by an interface 12 between the N layer 8 and the P<+> layer 7 at the surface. By these processes, a depletion layer is made to extend widely toward the N layer 8 low in impurity concentration and a breakdown strength can be remarkably improved. |
