MOS semiconductor device having gate insulating film containing nitrogen and method of manufacturing the same

Abstract

Disclosed is a MOS semiconductor device, which comprises a semiconductor substrate; a gate insulating film formed on the semiconductor substrate, the gate insulating film containing nitrogen; a gate electrode selectively formed on the gate insulating film; and an oxide film formed on a surface of the gate electrode and the semiconductor substrate, wherein a thickness of a first portion of the gate insulating film which overlaps vertically the gate electrode is one third or less that of a second portion of the gate insulating film disposed at a corner portion of the gate electrode. According to such constitution of the MOS transistor device of the present invention, by allowing the gate insulating film to contain nitrogen, an increase in a thickness of the gate insulating film toward the semiconductor substrate than required can be suppressed, and hence lowering of a gate voltage can be prevented, resulting in preventing a controllability deterioration of the MOS transistor device.

What is claimed is:  
     
         1 . A semiconductor device, comprising: 
 a semiconductor substrate;    a gate insulating film on said semiconductor substrate, the gate insulating film containing nitrogen;    a gate electrode on said gate insulating film; and    an oxide film on a surface of said gate electrode and said semiconductor substrate,    wherein said gate insulating film has a first portion under a center portion of said gate electrode and a second portion under an edge of said gate electrode, said second portion being thicker than said first portion, a first surface and a second surface of said first portion defining first and second parallel lines that intersect said second portion, said first parallel line being between said first portion and said substrate, said second parallel line being between said first portion and said gate electrode, a thickness of said second portion between said first parallel line and said substrate being one third or less than a thickness of said second portion between said second parallel line and said gate electrode.    
     
     
         2 . The semiconductor device according to  claim 1 , wherein said gate insulating film is an oxide film containing nitrogen at a concentration ranging from about 2 to 10%.  
     
     
         3 . The semiconductor device according to  claim 1 , wherein said gate insulating film has a nitrogen concentration showing a peak in near a surface of said semiconductor substrate.  
     
     
         4 . The semiconductor device according to  claim 1 , wherein said gate insulating film and said oxide film are formed in different steps.  
     
     
         5 . A semiconductor device, comprising: 
 a semiconductor substrate;    a gate insulating film on said semiconductor substrate, the gate insulating film containing nitrogen;    a gate electrode on said gate insulating film;    an oxide film on a surface of said gate electrode and said semiconductor substrate; and    a gate side wall film on a surface of said oxide film.    
     
     
         6 . The semiconductor device according to  claim 5 , wherein said gate insulating film located just under said gate electrode is an oxide film containing nitrogen at a concentration ranging from about 2 to 10%.  
     
     
         7 . The semiconductor device according to  claim 5 , wherein said gate insulating film has a nitrogen concentration showing a peak near a surface of said semiconductor substrate.  
     
     
         8 . The semiconductor device according to  claim 5 , wherein said gate insulating film has a first portion under a center portion of said gate electrode and a second portion under an edge of said gate electrode, said second portion being thicker than said first portion, a first surface and a second surface of said first portion defining first and second parallel lines that intersect said second portion, said first parallel line being between said first portion and said substrate, said second parallel line being between said first portion and said gate electrode, a thickness of said second portion between said first parallel line and said substrate being one third or less than a thickness of said second portion between said second parallel line and said gate electrode.  
     
     
         9 . A method for manufacturing for a semiconductor device, comprising the step of: 
 forming a gate insulating film on a semiconductor substrate, the gate insulating film containing nitrogen;    selectively forming a gate electrode on said gate insulating film; and    oxidizing said gate electrode and a surface of said semiconductor substrate, thus forming an oxide film on a surface of said gate electrode and a surface of said semiconductor substrate.    
     
     
         10 . The manufacturing method of a semiconductor device according to  claim 9 , wherein said gate insulating film has a first portion under a center portion of said gate electrode and a second portion under an edge of said gate electrode, said second portion being thicker than said first portion, a first surface and a second surface of said first portion defining first and second parallel lines that intersect said second portion, said first parallel line being between said first portion and said substrate, said second parallel line being between said first portion and said gate electrode, a thickness of said second portion between said first parallel line and said substrate being one third or less than a thickness of said second portion between said second parallel line and said gate electrode.  
     
     
         11 . The manufacturing method of a semiconductor device according to  claim 9 , wherein said gate insulating film located just under said gate electrode is an oxide film containing nitrogen at a concentration ranging from about 2% to 10%.  
     
     
         12 . The manufacturing method of a semiconductor device according to  claim 9 , wherein said gate insulating film has a nitrogen concentration showing a peak near a surface of said semiconductor substrate.  
     
     
         13 . The semiconductor device according to  claim 6 , 
 said semiconductor device further comprising: 
 a side wall film formed on a surface of said oxide film.  
   
     
     
         14 . The semiconductor device according to  claim 6 , 
 said semiconductor device further comprising: 
 said oxide film is post oxidation film.