Method for manufacturing semiconductor device

Abstract

A semiconductor device having an improved connecting reliability of an interconnect is presented via a simple and easy process, and further, a semiconductor device having a stable threshold voltage of a transistor that provide a stable electrical characteristic is also presented. A method for manufacturing a semiconductor device according to the present invention comprises: forming a trench in a silicon substrate; forming a first insulating film on a surface of said silicon substrate, said surface including an interior wall of said trench; forming a polysilicon film which plugged in said trench and covered on an entire surface of said silicon substrate; forming a second insulating film with oxidizing a portion of said polysilicon film disposed outside of said trench, and oxidizing a surface region of said silicon substrate located right under said first insulating film disposed outside of said trench and a surface region of said polysilicon film in said trench; and forming an embedded polysilicon layer with removing said second insulating film so that the surface of said silicon substrate is partially exposed and said polysilicon film is partially remained in said trench.

Dependencies are inferred from the claim text.