DIELECTRIC SEPARATION TYPE SEMICONDUCTOR DEVICE WHICH FORMS A RELATIVELY THICK AUXILIARY DIELECTRIC LAYER BENEATH A RELATIVELY THIN DIELECTRIC LAYER TO PREVENT THE DEGRADATION OF RESURF(REDUCED SURFACE FIELD) EFFECT AND TO IMPROVE SIMULTANEOUSLY VOLTAGE WITHSTANDING CAPABILITY

摘要

PURPOSE: A semiconductor device is provided to prevent the degradation of RESURF(REduced SURface Field) effect and to improve simultaneously voltage withstanding capability by forming a relatively thick auxiliary dielectric layer beneath a relatively thin dielectric layer. CONSTITUTION: A main dielectric layer(3-1) is formed on the entire surface of a semiconductor substrate(1). A first semiconductor layer(2) is formed on the substrate via the main dielectric. A second semiconductor layer(4) is selectively formed on the first semiconductor layer. The third semiconductor layer(5) is formed along a periphery of the first semiconductor layer. The third semiconductor layer is slightly spaced apart from the periphery of the first semiconductor layer. A ring-like insulating layer(9) surrounds the third semiconductor layer. A first main electrode(6) is formed on the second semiconductor layer. A second main electrode(7) is formed on the third semiconductor layer. A first auxiliary dielectric layer(3-2) is formed beneath the main dielectric layer. The first auxiliary dielectric layer is relatively thicker than the main dielectric layer. The area of the first auxiliary dielectric layer is smaller than that of the main dielectric layer.