Process for preparing semiconductor device using a tunnel oxidized layer

Abstract

A process for preparing a semiconductor device forms an insulating thin film capable of tunnelling phenomenon of carriers on a semiconductor substrate and forms a polycrystalline semiconductor layer on the thin film. An impurity is injected to the surface of the polycrystalline semiconductor layer, the diffusion coefficient to the thin film being smaller than that to the polycrystalline semiconductor layer. The process effects a first heat treatment at a temperature of 800.degree. C. or less to diffuse the impurity injected into the polycrystalline semiconductor layer in the polycrystalline semiconductor layer, thereby forming a uniform or substantially uniform impurity containing region at least at the thin film side of the polycrystalline semiconductor layer, and, effects a second heat treatment the temperature of which is 950.degree. C. or less and higher than the temperature of the first heat treatment to diffuse the impurity present in the polycrystalline semiconductor layer into the semiconductor substrate through the thin film, thereby forming a diffused layer.

Dependencies are inferred from the claim text.