Method of manufacturing a semiconductor integrated circuit device

Abstract

A method of manufacturing a semiconductor integrated circuit device comprising forming a silicon oxide film as thin as 5 nm or less on the surfaces of p type wells and n type wells by wet oxidizing a substrate, heating the substrate in an atmosphere containing about 5% of an NO gas to introduce nitrogen into the silicon oxide film so as to form a silicon oxynitride film, exposing the substrate to a nitrogen plasma atmosphere to further introduce nitrogen into the silicon oxynitride film in order to form a silicon oxynitride gate insulating film having a first peak concentration near the interface with the substrate and a second peak concentration near the surface thereof. Thereby, the concentration of nitrogen in the gate insulating film is increased without raising the concentration of nitrogen near the interface between the substrate and the gate insulating film to a higher level than required.

1 . A semiconductor integrated circuit device having a MISFET, comprising: 
 (a) a gate insulating film of the MISFET formed over a semiconductor substrate, wherein the gate insulating film is formed of a silicon oxide film, an interface being formed between the semiconductor substrate and the gate insulating film;    (b) a gate electrode of the MISFET formed over the gate insulating film, an interface being formed between the gate insulating film and the gate electrode;    (c) semiconductor areas for source and drain regions of the MISFET in the semiconductor substrate;    wherein the gate insulating film has a first peak concentration of nitrogen near the interface between the semiconductor substrate and the gate insulating film and a second peak concentration of nitrogen near the interface between the gate insulating film and the gate electrode; and    wherein the second peak concentration is higher than the first peak concentration.    
   
   
       2 . A semiconductor integrated circuit device according to  claim 1 , wherein the second peak concentration is made higher than 10 atomic %.  
   
   
       3 . A semiconductor integrated circuit device according to  claim 1 , wherein the first peak concentration of the nitrogen is in a range of 1 to 10 atomic %.  
   
   
       4 . A semiconductor integrated circuit device according to  claim 1 , wherein the gate insulating film has a thickness of 5 nm or less.  
   
   
       5 . A semiconductor integrated circuit device having a p-type MISFET; comprising: 
 (a) a gate insulating film of the p-type MISFET formed over a semiconductor substrate, wherein the gate insulating film is formed of a silicon oxide film, an interface being formed between the semiconductor substrate and the gate insulating film;    (b) a gate electrode of the p-type MISFET formed over the gate insulating film, wherein the gate electrode is doped with boron, an interface being formed between the gate insulating film and the gate electrode; and    (c) semiconductor areas for source and drain regions of the p-type MISFET in the semiconductor substrate;    wherein the gate insulating film has a first peak concentration of nitrogen near the interface between the semiconductor substrate and the gate insulating film and a second peak concentration of nitrogen near the interface between the gate insulating film and the gate electrode; and    wherein the second peak concentration is higher than the first peak concentration.    
   
   
       6 . A semiconductor integrated circuit device according to  claim 5 , wherein the second peak concentration is made higher than 10 atomic %.  
   
   
       7 . A semiconductor integrated circuit device according to  claim 5 , wherein the first peak concentration of the nitrogen is in the range of 1 to 10 atomic %.  
   
   
       8 . A semiconductor integrated circuit device according to  claim 5 , wherein the gate insulating film has a thickness of 5 nm or less.