Semiconductor device and manufacturing method for semiconductor device

Abstract

A semiconductor device has: a semiconductor substrate; a trench that extends from a first surface of the semiconductor substrate towards an interior of the semiconductor substrate, and that has a recess/protrusion structure on a side wall surface thereof; a semiconductor film that is formed so as to cover the side wall surface of the trench, be continuous with the side wall surface, and extend onto the first surface of the semiconductor substrate; an opposite electrode having a first portion that is provided at a position opposing the semiconductor substrate while sandwiching the semiconductor film therebetween, and that extends on the first surface of the semiconductor substrate, and a second portion that is continuous with the first portion and extends so as to fill the trench; and an insulating film that insulates the semiconductor film from the opposite electrode.

What is claimed is: 
     
         1 . A manufacturing method for a semiconductor device, comprising:
 a step of forming a trench that extends towards an interior of a semiconductor substrate from a first surface of the semiconductor substrate through Bosch etching;   a step of forming a semiconductor film so as to cover a side wall surface of the trench, be continuous with the side wall surface, and extend onto the first surface of the semiconductor substrate;   a step of forming an insulating film on a surface of the semiconductor film; and   a step of forming, on the insulating film, an opposite electrode having a first portion that extends on the first surface of the semiconductor substrate and a second portion that is continuous with the first portion and extends so as to fill the trench.   
     
     
         2 . The manufacturing method for a semiconductor device according to  claim 1 , further comprising:
 a step of performing heat annealing after the step of forming the insulating film.   
     
     
         3 . The manufacturing method for a semiconductor device according to  claim 2 ,
 wherein the step of forming the semiconductor film includes:   a first step of forming a first polysilicon film doped with impurities; and   a second step of forming a non-doped second polysilicon film on a surface of the first polysilicon film.   
     
     
         4 . The manufacturing method for a semiconductor device according to  claim 2 ,
 wherein the step of forming the semiconductor film includes:   a first step of forming a first polysilicon film doped with impurities;   a second step of forming a non-doped second polysilicon film on a surface of the first polysilicon film; and   a third step of forming a rough-surfaced polysilicon film on a surface of the second polysilicon film.