Semiconductor memory and manufacturing method thereof

Abstract

A buried strap is formed after forming an SiC layer on the side surface of a trench in order to suppress the epitaxial growth of Si from the side surface (single crystal Si) of the trench to the buried strap (polycrystalline Si) without causing an increase in the contact resistance in the post process accompanied by high temperature after formation of the buried strap.

1 . A semiconductor device comprising: 
 a single crystal semiconductor substrate;    a polycrystalline semiconductor film formed on said single crystal semiconductor substrate; and    a conductive interface layer formed between said single crystal semiconductor substrate and said polycrystalline semiconductor film and formed of a material different from constituent materials of said single crystal semiconductor substrate and said polycrystalline semiconductor film.    
     
     
         2 . The semiconductor device according to  claim 1 , wherein a trench is formed in the surface of said single crystal semiconductor substrate, said polycrystalline semiconductor film is formed in said trench, and said interface layer is formed between the side wall of said trench and said polycrystalline semiconductor film.  
     
     
         3 . The semiconductor device according to  claim 2 , wherein said single crystal semiconductor substrate is formed of a single crystal silicon substrate, said polycrystalline semiconductor film is formed of a polysilicon film, and said interface layer is formed of a silicon carbide layer.  
     
     
         4 . The semiconductor device according to  claim 3 , wherein the thickness of said silicon carbide layer is set to not larger than 10 nm.  
     
     
         5 . The semiconductor device according to  claim 2 , wherein said single crystal semiconductor substrate is formed of a single crystal silicon substrate, said polycrystalline semiconductor film is formed of a polysilicon film, and said interface layer is formed of a silicon nitride layer having an S/N ratio of not larger than 1.24.  
     
     
         6 . The semiconductor device according to  claim 2 , wherein said single crystal semiconductor substrate is formed of a single crystal silicon substrate, said polycrystalline semiconductor film is formed of a polysilicon film, and said interface layer is formed of silicon nitride layer having chlorine concentration of not less than 4×10 20  cm −3 .  
     
     
         7 . The semiconductor device according to  claim 2 , wherein said single crystal semiconductor substrate is formed of a single crystal silicon substrate, said polycrystalline semiconductor film is formed of a polysilicon film, and said interface layer is formed of silicon nitride layer having an S/N ratio of not larger than 1.24 and a chlorine concentration of not less than 4×10 20  cm −3 .  
     
     
         8 . The semiconductor device according to  claim 2 , wherein a diffusion layer connected to said polycrystalline semiconductor film by said interface layer is formed on the surface of said single crystal semiconductor substrate and a conductive body connected to said polycrystalline semiconductor film is formed in said single crystal semiconductor substrate.  
     
     
         9 . The semiconductor device according to  claim 8 , wherein said diffusion layer is a source/drain diffusion layer of a MOS transistor and said conductive body is a storage node electrode of a trench capacitor.  
     
     
         10 . A method for manufacturing a semiconductor device comprising the steps of: 
 forming a conductive interface layer on the surface of a single crystal semiconductor substrate by reacting gas of a material different from a constituent material of the single crystal semiconductor substrate with the single crystal semiconductor substrate; and    forming a polycrystalline semiconductor film formed of a material different from a constituent material of the interface layer and connected to the single crystal semiconductor substrate by the interface layer.    
     
     
         11 . The method for manufacturing the semiconductor device according to  claim 10 , wherein the gas is gas containing carbon.  
     
     
         12 . The method for manufacturing the semiconductor device according to  claim 11 , wherein the carbon containing gas is C 2 H 4  gas.  
     
     
         13 . A method for manufacturing a semiconductor device comprising the steps of: 
 forming a conductive interface layer on a single crystal semiconductor substrate by use of a CVD method using a material different from a constituent material of the single crystal semiconductor substrate as a raw material; and    forming a polycrystalline semiconductor film formed of a material different from a constituent material of the interface layer and connected to the single crystal semiconductor substrate by the interface layer.    
     
     
         14 . The method for manufacturing the semiconductor device according to  claim 13 , wherein the raw material is a material containing a compound having an Si-Si bond and Si-Cl bond, the CVD method is an LPCVD method and the interface layer is a silicon nitride layer.  
     
     
         15 . The method for manufacturing the semiconductor device according to  claim 14 , wherein Si n Cl 2n+2  (n is a positive integer larger than 1) or Si m Cl 2m+2−x H x  (m is a positive integer larger than 1 and x is a positive integer less than 2m+2) is used as the compound.  
     
     
         16 . The method for manufacturing the semiconductor device according to  claim 14 , wherein Si 2 Cl 6  and NH 3  are used as the raw material and the film formation temperature of the silicon nitride layer is set to not higher than 650° C.  
     
     
         17 . The method for manufacturing the semiconductor device according to  claim 14 , wherein a single crystal silicon substrate is used as the single crystal semiconductor substrate and a polysilicon film is used as the polycrystalline semiconductor film.  
     
     
         18 . A method for manufacturing a semiconductor device, comprising the steps of: 
 repeatedly adsorbing SiCl 4  to a surface of a single-crystal silicon substrate and nitriding the surface of the single-crystal silicon substrate thereby forming an interface layer of silicon nitride on the surface of the single-crystal silicon substrate; and    forming a polycrystalline silicon film connected to the single-crystal silicon substrate by the interface layer.    
     
     
         19 . A method for manufacturing a semiconductor device comprising the steps of: 
 forming a trench in the surface of a single crystal semiconductor substrate;    covering a portion of the side surface of the trench which is lower than the opening of the trench with an insulating film and filling a conductive material into a portion of the trench which is lower than the opening;    forming a conductive interface layer formed of a material different from a constituent material of the single crystal semiconductor substrate on the side surface of a portion of the trench which is not filled with the conductive material; and    filling a polycrystalline semiconductor film formed of a material different from a constituent material of the interface layer into the trench.    
     
     
         20 . The method for manufacturing the semiconductor device according to  claim 18 , wherein the interface layer is formed by reacting gas of a material different from the constituent material of the single crystal semiconductor substrate with the single crystal semiconductor substrate.  
     
     
         21 . The method for manufacturing the semiconductor device according to  claim 19 , wherein the interface layer is formed by use of a CVD method using a material different from the constituent material of the single crystal semiconductor substrate as a raw material.