Semiconductor device and method of manufacturing the same

Abstract

A gate dielectric film, a poly-silicon film, a film of a refractory metal such as tungsten, and a gate cap dielectric film are sequentially laminated on a semiconductor substrate. The gate cap dielectric film and the refractory metal film are selectively removed by etching. Thereafter, a double protection film including a silicon nitride film and a silicon oxide film is formed on side surfaces of the gate cap dielectric film, the refractory metal film, and the poly-silicon film. The poly-silicon film is etched using the double protection film as a mask. Thereafter, the semiconductor substrate is light oxidized to form a silicon oxide film on side surfaces of the poly-silicon film. Accordingly, a junction leakage of a MOSFET having a gate electrode of a poly-metal structure, particularly, a memory cell transistor of a DRAM, can be further reduced.

1 . A semiconductor device, comprising: 
 a semiconductor substrate;    a gate dielectric film formed on the semiconductor substrate;    a poly-metal gate electrode having at least a poly-silicon film and a refractory metal film formed on the gate dielectric film;    a gate cap that covers an upper surface of the poly-metal gate electrode; and    a sidewall that covers side surfaces of the poly-metal gate electrode,    wherein the sidewall has a multilayer structure including at least a first dielectric film and a second dielectric film made of a material different from that of the first dielectric film, and the first dielectric film has a vertical part that is in contact with the side surfaces of the poly-metal gate electrode and a horizontal part that extends substantially parallel with a front surface of the semiconductor substrate from the gate dielectric film side end at the vertical part.    
   
   
       2 . The semiconductor device as claimed in  claim 1 , wherein the second dielectric film is in contact with both the vertical and the horizontal part of the first dielectric film.  
   
   
       3 . The semiconductor device as claimed in  claim 1 , wherein the poly-silicon film locates at the side of the gate dielectric film and the refractory metal film locates at the side of the gate cap.  
   
   
       4 . The semiconductor device as claimed in  claim 2 , wherein the poly-silicon film locates at the side of the gate dielectric film and the refractory metal film locates at the side of the gate cap.  
   
   
       5 . The semiconductor device as claimed in  claim 3  further comprise a light oxide film formed between the horizontal part of the first dielectric film and the gate dielectric film.  
   
   
       6 . The semiconductor device as claimed in  claim 4  further comprise a light oxide film formed between the horizontal part of the first dielectric film and the gate dielectric film.  
   
   
       7 . The semiconductor device as claimed in  claim 3 , wherein the cross sectional form of the poly-silicon film has a projection by removing the corner of the poly-silicon film located at the side of the refractory metal film.  
   
   
       8 . The semiconductor device as claimed in  claim 4 , wherein the cross sectional form of the poly-silicon film has a projection by removing the corner of the poly-silicon film located at the side of the refractory metal film.  
   
   
       9 . The semiconductor device as claimed in  claim 5 , wherein the cross sectional form of the poly-silicon film has a projection by removing the corner of the poly-silicon film located at the side of the refractory metal film.  
   
   
       10 . The semiconductor device as claimed in  claim 6 , wherein the cross sectional form of the poly-silicon film has a projection by removing the corner of the poly-silicon film located at the side of the refractory metal film.  
   
   
       11 . The semiconductor device as claimed in  claim 1 , wherein the first dielectric film consists of a silicon nitride film, the second dielectric film consists of a silicon oxide film, and the refractory metal film consists of a tungsten film.  
   
   
       12 . The semiconductor device as claimed in  claim 2 , wherein the first dielectric film consists of a silicon nitride film, the second dielectric film consists of a silicon oxide film, and the refractory metal film consists of a tungsten film.  
   
   
       13 . The semiconductor device as claimed in  claim 4 , wherein the first dielectric film consists of a silicon nitride film, the second dielectric film consists of a silicon oxide film, and the refractory metal film consists of a tungsten film.  
   
   
       14 . The semiconductor device as claimed in  claim 6 , wherein the first dielectric film consists of a silicon nitride film, the second dielectric film consists of a silicon oxide film, and the refractory metal film consists of a tungsten film.  
   
   
       15 . The semiconductor device as claimed in  claim 10 , wherein the first dielectric film consists of a silicon nitride film, the second dielectric film consists of a silicon oxide film, and the refractory metal film consists of a tungsten film.  
   
   
       16 . The semiconductor device as claimed in  claim 15 , the poly-metal gate electrode is the gate electrode of a memory cell transistor of a DRAM.  
   
   
       17 . A method of manufacturing a semiconductor device, comprising: 
 a first step of forming a gate dielectric film on a semiconductor substrate;    a second step of forming at least a poly-silicon film and a refractory metal film on the gate dielectric film;    a third step of patterning at least the refractory metal film;    a fourth step of forming a sidewall having a multilayer structure on side surfaces of the patterned refractory metal film;    a fifth step of patterning the poly-silicon film; and    a sixth step of oxidizing the side surfaces of the patterned poly-silicon film.    
   
   
       18 . The method of manufacturing the semiconductor device as claimed in  claim 17 , wherein the fourth step include: 
 a step of depositing a silicon nitride film;    a step of depositing a silicon oxide film on the silicon nitride film;    a step of etching back the silicon oxide film; and    a step of etching the silicon nitride film using the silicon oxide film as a mask.    
   
   
       19 . The method of manufacturing the semiconductor device as claimed in  claim 17 , wherein the fifth step consists of the step of patterning the poly-silicon film using the sidewall as a musk.  
   
   
       20 . The method of manufacturing the semiconductor device as claimed in  claim 18 , wherein the fifth step consists of the step of patterning the poly-silicon film using the sidewall as a musk.