| 摘要 |
PURPOSE:To minimize the variation of breakdown voltages by eliminating the breakdown at the surface and generating breakdown inside a semiconductor by a method wherein an N type diffused layer is so formed as to cover the surface region of a P type diffused layer, thus constituting a zener diode. CONSTITUTION:An N type epitaxial layer 35 on the surface of a P type semiconductor substrate 36 is surrounded by an isolation layer 34 composed of a P<+> type diffused layer, and a P<+> type diffused layer 34A is formed at a part. The P<+> diffused layer 33 is formed, the surface thereof is covered, and then an N<+> type diffused layer 32 extending to the N type epitaxial layer 35 is formed. A P-N junction composed between the N<+> diffused layer 32 and the P<+> type diffused layer 33 is not exposed to the surface, and the breakdown place becomes immediately under 37 the region of the N<+> type diffused layer 32 or toward the center therefrom, resulting in breakdown inside; therefore, a breakdown voltage is obtained independently at all of the influence by an oxide film on the surface and the surface level, and changes with time and the change due to thermal history become minimum. |
