JPS6481268A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To manufacture a semiconductor device having a good characteristic with the small number of processes by a method wherein a low-melting-point glass layer is melted by a heat treatment, an insulating layer is formed around a polysilicon layer and an impurity inside the low-melting-point glass layer is diffused into a substrate in order to form a diffusion region of low impurity concentration which is interlinked with a source region and a drain region of high impurity concentration. CONSTITUTION:A gate oxide film 11, a polysilicon layer 12 and a low-melting-point layer, e.g., a phosphate glass layer 13, are laminated in succession on a p-type silicon substrate 10. Then, only the phospho-glass layer 13 is removed selectively by an anisotropic etching operation. After that, the polysilicon layer 12 under it is removed selectively by a quasi-isotropic etching operation of a high selective rate. At this stage, ions of an impurity are implanted by making use of the phosphate glass layer 13 as a mask; a source region 14 and a drain region 151 (n<+> diffusion regions) of high impurity concentration are formed. Then, if the phospho-glass layer 13 is melted by a heat treatment, an insulating layer is formed around the polysilicon layer 12 functioning as a gate; phosphorus inside the glass layer 13 is diffused into the substrate 10; a source region 142 and a drain region 152 (n regions) of low impurity concentration are formed.