Semiconductor device and manufacturing method thereof

Abstract

A deep trench is formed in a silicon substrate. The inner surface of the trench is next coated with a thin polycrystalline silicon film (liner film) so as not to close the trench. A silicon germanium film (node electrode) is then formed on the thin polycrystalline silicon film so as not to close the trench. Next, a heat treatment is performed on the silicon germanium film thereby to flow only the silicon germanium so that the trench is filled.

What is claimed is:  
     
         1 . A semiconductor device comprising: 
 a silicon substrate having a trench formed in a surface of the silicon substrate;    a polycrystalline silicon film coating an inner surface of the trench such that the trench is not closed; and    a conductive film made of material having a lower melting point than silicon and formed on the polycrystalline silicon film so as to fill the trench.    
     
     
         2 . A semiconductor device according to  claim 1 , wherein the conductive film is a node electrode of a trench capacitor.  
     
     
         3 . A semiconductor device according to  claim 1 , wherein the material is either silicon germanium or germanium.  
     
     
         4 . A semiconductor device according to  claim 1 , wherein the conductive film is a Si 1-X Ge X  film (X>1.5) containing boron.  
     
     
         5 . A semiconductor device according to  claim 1 , wherein the conductive film is a Si 1-x Ge X  film (X<0.45) containing phosphorus.  
     
     
         6 . A semiconductor device according to  claim 1 , wherein an aspect ratio of the trench is 10 or more.  
     
     
         7 . A method of manufacturing a semiconductor device, comprising steps of: 
 forming a trench on a surface of a silicon substrate;    coating an inner surface of the trench with a polycrystalline silicon film as a liner film such that the trench is not closed;    forming a conductive film made of material having a lower melting point than silicon, on the polycrystalline silicon film, such that the trench is not closed; and    flowing the conductive film so as to fill the trench, by performing a heat treatment on the conductive film.    
     
     
         8 . A method according to  claim 7 , wherein the conductive film is a node electrode of a trench capacitor.  
     
     
         9 . A method according to  claim 7 , wherein the material is either a silicon germanium or germanium.  
     
     
         10 . A method according to  claim 7 , wherein the conductive film is a Si 1-X Ge X  film (X>1.5) containing boron.  
     
     
         11 . A method for according to  claim 7 , wherein the conductive film is a Si 1-X Ge X  film (X<0.45) containing phosphorus.  
     
     
         12 . A method according to  claim 7 , wherein an aspect ratio of the trench is 10 or more.  
     
     
         13 . A method according to  claim 7 , wherein the conductive film is formed in an amorphous state on the polycrystalline silicon film and is thereafter changed into polycrystalline after the heat treatment.  
     
     
         14 . A method according to  claim 7 , wherein the heat treatment is at a temperature higher than a temperature at which the conductive film is formed.  
     
     
         15 . A method according to  claim 7 , wherein a pressure of the heat treatment is set higher than a pressure at which the conductive film is formed, and partial pressures of oxygen and water vapor in an atmosphere during formation of the conductive film and a heat treatment thereof are set low than a main gas in the atmosphere, thereby to attain a state in which an oxide film does not substantially exist on a surface of the conductive film.  
     
     
         16 . A method according to  claim 7 , wherein an atmosphere during the heat treatment is either a hydrogen atmosphere or an inactive gas atmosphere.