JPS6480073A - Semiconductor device - Google Patents

Abstract

PURPOSE:To assure the stable high dielectric breakdown voltage by a method wherein the growth of depletion layers is accelerated by the effects of field plate and research structure while the same conductivity type layer in high impurity concentration is provided below the end of said plate through the intermediary of an insulating layer. CONSTITUTION:A conductive layer wherein a contact hole 31 is in contact with a p<+>region 2 (the second region) becomes a field plate 4 while a depletion layer 10 extends from the rear side of the conductive layer. Besides, another depletion layer 20 formed in research structure extends in the side near a PN junction 52 between an n region 1 and a p layer 6 in low concentration in contact with the n region 1. The dielectric breakdown voltage is stabilized not affected by any surface state by the actions of these two depletion layers 10, 20 while the ends of depletion layers 10, 20 are kept away from the PN junction 51 to moderate the electric field impressed on the PN junction 51 under voltage in the reverse direction. Furthermore, an n<+>region 7 in impurity concentration higher than that in the n region 1 is formed below the end of the plate 4 while the depletion layer 10 stops in this n<+>region 7 so that the electric field may not concentrate in the region 7 in low resistance causing no dielectric breakdown in this part.