Semiconductor substrate with defects reduced or removed and method of manufacturing the same, and semiconductor device capable of bidirectionally retaining breakdown voltage and method of manufacturing the same

Abstract

An N-type silicon substrate () has a bottom surface and an upper surface which are opposed to each other. In the bottom surface of the N-type silicon substrate (), a P-type impurity diffusion layer () of high concentration is entirely formed by diffusing a P-type impurity. In the upper surface of the N-type silicon substrate (), a P-type isolation region () is partially formed by diffusing a P-type impurity. The P-type isolation region () has a bottom surface reaching an upper surface of the P-type impurity diffusion layer (). As viewed from the upper surface side of the N-type silicon substrate (), the P-type isolation region () is formed, surrounding an Nregion () which is part of the N-type silicon substrate (). The Nregion () surrounded by the P-type isolation region () is defined as an element formation region of the N-type silicon substrate (). Thus obtained are a semiconductor device and a method of manufacturing the same, and a semiconductor substrate and a method of manufacturing the same, which make it possible to retain bidirectional breakdown voltages and ensure high reliability.