Method of manufacturing a semiconductor device

摘要

A method for manufacturing a semiconductor device having a high breakdown voltage and a high reliability, comprises (a) forming on a semiconductor substrate an insulating layer having a diffusion window; (b) forming an impurity-doped poly-silicon layer on the insulating layer and on that portion of the semiconductor substrate which is exposed through the diffusion window; (c) forming an undoped poly-silicon layer on the impurity-doped poly-silicon layer; (d) thermally oxidizing the substrate with the insulating layer, impurity-doped poly-silicon layer and undoped poly-silicon layer, thus diffusing the impurity from the impurity-doped poly-silicon layer into the semiconductor substrate through the diffusion window and converting the undoped poly-silicon layer to a silicon oxide layer; (e) forming on the silicon oxide layer an oxidation-resisting mask layer in a desired pattern; and (f) thermally oxidizing the substrate with the insulating layer, impurity-doped poly-silicon layer, silicon oxide layer and mask layer, thus converting those portions of the impurity-doped poly-silicon layer which lie beneath those portions of the silicon oxide layer which are exposed through the mask layer to impurity-doped silicon oxide layers, whereby the remaining portions of the impurity-doped poly-silicon layer provide an interconnection electrode layer having a desired pattern.