Semiconductor device and manufacturing method thereof

Abstract

A gate oxide film is formed on a silicon substrate, and a gate electrode is formed on the oxide film. The gate electrode is a polysilicon film that is given p + conductivity because of doping with B. An Si 3 N 4 film is formed on the top surface of the gate electrode and sidewall spacers of Si 3 N 4 are formed on the side walls of the gate electrode. An interlayer insulating film of SiO 2 is formed on the Si 3 N 4 film, the sidewall spacers, and a LOCOS oxide film. This structure inhibits diffusion of B from the gate electrode to the interlayer insulating film in a heating process that is executed after the formation of the gate electrode.

What is claimed is:  
     
         1 . A semiconductor device comprising: 
 a gate electrode that is formed on a semiconductor substrate via a gate insulating film and in which an impurity is introduced at a high concentration;    an insulating or conductive film containing nitrogen that is formed on a top surface and side walls of the gate electrode; and    an interlayer insulating film formed on the insulating or conductive film and containing at least SiO 2 .    
     
     
         2 . The semiconductor device according to  claim 1 , wherein the gate electrode is made of p +  polysilicon.  
     
     
         3 . The semiconductor device according to  claim 1 , wherein the gate electrode is a two-layer polycide structure of WSi x  and polysilicon.  
     
     
         4 . The semiconductor device according to  claim 1 , wherein the gate electrode is a silicide single layer.  
     
     
         5 . The semiconductor device according to  claim 1 , wherein the impurity is boron.  
     
     
         6 . The semiconductor device according to  claim 1 , wherein the insulating film containing nitrogen is an Si 3 N 4  film or an SiON film deposited by LPCVD or plasma CVD.  
     
     
         7 . The semiconductor device according to  claim 1 , wherein the insulating film containing nitrogen has a two-layer structure of an Si 3 N 4  film or an SiON film deposited by LPCVD or plasma CVD and an SiO 2  film.  
     
     
         8 . The semiconductor device according to  claim 1 , wherein the gate insulating film is an oxynitride film formed by nitriding an oxide film.  
     
     
         9 . A manufacturing method of a semiconductor device, comprising the steps of: 
 forming a gate insulating film on a semiconductor device;    depositing a conductive film on the gate insulating film;    introducing an impurity into the conductive film;    depositing a first insulating film containing nitrogen on the conductive film;    processing the conductive film and the first insulating film into a pattern in which a remaining portion of the first insulating film exists on a remaining portion of the conductive film that is a gate electrode;    forming a second insulating film containing nitrogen on side walls of the remaining first insulating film and the gate electrode; and    depositing an interlayer insulating film of SiO 2  on the second insulating film.    
     
     
         10 . The manufacturing method according to  claim 9 , wherein the impurity is boron.  
     
     
         11 . The manufacturing method according to  claim 9 , wherein the conductive film is made of p +  polysilicon.  
     
     
         12 . The manufacturing method according to  claim 9 , wherein each of the first and second insulating films is an Si 3 N 4  film or an SiON film deposited by LPCVD or plasma CVD.  
     
     
         13 . The manufacturing method according to  claim 9 , wherein each of the first and second insulating films has a two-layer structure of an Si 3 N 4  film or an SiON film deposited by LPCVD or plasma CVD and an SiO 2  film.  
     
     
         14 . A manufacturing method of a semiconductor device, comprising the steps of: 
 forming a gate insulating film on a semiconductor substrate;    depositing a refractory metal silicide film on the gate insulating film;    forming a thin film for preventing impurity outward diffusion on the refractory metal silicide film; and    introducing an impurity into the refractory metal silicide film through the thin film.    
     
     
         15 . The manufacturing method according to  claim 14 , wherein the thin film is an Si 3 N 4  film formed by LPCVD.  
     
     
         16 . The manufacturing method according to  claim 14 , wherein the thin film is a metal nitride film formed by directly nitriding the refractory metal silicide film.  
     
     
         17 . The manufacturing method according to  claim 14 , wherein the refractory metal silicide film is a WSi x  film or a MoSi x  film.  
     
     
         18 . A manufacturing method of a semiconductor device, comprising the steps of: 
 forming a gate insulating film on a semiconductor substrate;    depositing a refractory metal silicide film on the gate insulating film;    patterning the refractory metal silicide film into a gate electrode;    forming a thin film for preventing impurity outward diffusion on all or part of surfaces of the gate electrode; and    introducing an impurity into the gate electrode through the thin film.    
     
     
         19 . The manufacturing method according to  claim 18 , wherein the thin film is an Si 3 N 4  film formed by LPCVD.  
     
     
         20 . The manufacturing method according to  claim 18 , wherein the thin film is a metal nitride film formed by directly nitriding the gate electrode.  
     
     
         21 . The manufacturing method according to  claim 18 , wherein the refractory metal silicide film is a WSi x  film or a MoSi x  film.