Semiconductor device and method for manufacturing the same

Abstract

A silicon oxide film with a film thickness of 5 to 7 nm is formed on a first region, a silicon oxynitride film with a film thickness of 2 to 3 nm, and a nitrogen concentration of 1 to 3 atom % is formed on a second region, and a silicon oxynitride film with a film thickness of 1 to 2 nm, and a nitrogen concentration of 3 to 5 atom % is formed on a third region on a silicon substrate. Then, radical nitriding is applied to the silicon oxide film, and the silicon oxynitride films.

What is claimed is:  
     
         1 . A semiconductor device comprising: 
 a semiconductor substrate; and    a plurality of types of transistors provided with gate dielectric films different in film thickness and nitrogen concentration from one another, wherein said gate dielectric film having a higher film thickness has a higher nitrogen concentration.    
     
     
         2 . The semiconductor device according to  claim 1 , wherein said gate dielectric films are formed by forming a plurality of types of dielectric films different in film thickness and nitrogen concentration from one another, and applying radical nitriding to the dielectric films.  
     
     
         3 . The semiconductor device according to  claim 1 , wherein the types of the gate dielectric films are three, a first gate dielectric film has a film thickness of 5 to 7 nm, and a nitrogen concentration of 10 to 15 atom %, a second gate dielectric film has a film thickness of 2 to 3 nm, and a nitrogen concentration of 8 to 12 atom %, and a third gate dielectric film has a film thickness of 1 to 2 nm, and a nitrogen concentration of 6 to 10 atom %.  
     
     
         4 . A semiconductor device comprising: 
 a semiconductor substrate; and    a plurality of types of transistors provided with gate dielectric films different in film thickness and nitrogen concentration from one another, wherein said gate dielectric films are formed by forming a plurality of types of dielectric films different in film thickness and nitrogen concentration from one another, and applying radical nitriding to the dielectric films such that nitrogen does not reach an interface between the dielectric films and said semiconductor substrate, and non-radical nitrided layers are provided on a side in contact with said semiconductor substrate.    
     
     
         5 . The semiconductor device according to  claim 1 , wherein said gate dielectric films consist of silicon oxynitride, hafnium nitride, or alumina nitride.  
     
     
         6 . A method for manufacturing a semiconductor device, comprising the steps of: 
 forming a plurality of types of dielectric films different in film thickness and nitrogen concentration from one another on a semiconductor substrate; and    applying radical nitriding to said dielectric films to form a plurality of types of gate dielectric films.    
     
     
         7 . The method for manufacturing a semiconductor device according to  claim 6 , wherein said dielectric films are formed such that the dielectric film with a lower film thickness has a higher nitrogen concentration.  
     
     
         8 . The method for manufacturing a semiconductor device according to  claim 7 , wherein said gate dielectric films are formed such that the gate dielectric film with a higher film thickness has a higher nitrogen concentration.  
     
     
         9 . The method for manufacturing a semiconductor device according to  claim 7 , wherein said step of forming the dielectric films comprises the steps of: 
 dividing a surface of said semiconductor substrate into a plurality of regions, and forming a first dielectric film so as to cover the individual regions; and    selectively removing the first dielectric film formed on a second region, and forming a second dielectric film with a lower film thickness and a higher nitrogen concentration than said first dielectric film on said second region.    
     
     
         10 . The method for manufacturing a semiconductor device according to  claim 9 , wherein the dielectric film formed on an nth ((n) is a natural number equal to or more than 3) region is removed, and a dielectric film with a lower film thickness and a higher nitrogen concentration than a dielectric film ford on an (n−1)th region is formed on the nth region after said second dielectric film is formed.  
     
     
         11 . The method for manufacturing a semiconductor device according to  claim 7 , wherein said step for forming the dielectric films comprises the steps of: 
 dividing a surface of said semiconductor substrate into a plurality of regions, and forming a first dielectric film so as to cover the individual regions; and    selectively removing the first dielectric film formed on a second region, and forming a second dielectric film with a higher film thickness and a lower nitrogen concentration than said first dielectric film on said second region.    
     
     
         12 . The method for manufacturing a semiconductor device according to  claim 11 , wherein the dielectric film formed on an nth ((n) is a natural number equal to 3 or more) region is removed, and a dielectric film with a higher film thickness and a lower nitrogen concentration than a dielectric film formed on an (n−1)th region is formed on the nth region after said second dielectric film is formed.  
     
     
         13 . The method for manufacturing a semiconductor device according to  claim 12 , wherein a protection film is formed on the dielectric films formed on the first to (n−1)th regions to prevent the dielectric film formed on the nth region from being foamed on these regions when the dielectric film is formed on the nth region.  
     
     
         14 . The method for manufacturing a semiconductor device according to  claim 6 , wherein said semiconductor substrate is a silicon substrate, and a surface layer of said silicon substrate is oxidized or oxynitrided to form a silicon oxide or oxynitride film serving as said dielectric film.  
     
     
         15 . The method for manufacturing a semiconductor device according to  claim 6 , wherein said semiconductor substrate is a silicon substrate, the types of said dielectric films are three, and forming said three types of dielectric films comprises the steps of: 
 applying oxidizing or oxynitriding to a surface of said silicon substrate to form a first silicon oxide or oxynitride film so as to cover first to third regions on the surface of said silicon substrate;    forming a first resist covering said first and third regions, and having an opening on said second region;    etching said first silicon oxide or oxynitride film using said first resist as a mask to remove said first silicon oxide or oxynitride film formed on said second region;    removing said first resist;    applying oxynitriding to the surface of said silicon substrate to form a second silicon oxynitride film with a lower film thickness and a higher nitrogen concentration than said first silicon oxide or oxynitride film on said second region;    forming a second resist covering said first and second regions, and having an opening on said third region;    etching said first silicon oxide or oxynitride film using said second resist as a mask to remove said first silicon oxide or oxynitride film formed on said third region;    removing said second resist; and    applying oxynitriding to the surface of said silicon substrate to form a third silicon oxynitride film with a lower film thickness and a higher nitrogen concentration than said second silicon oxynitride film on said third region.    
     
     
         16 . The method for manufacturing a semiconductor device according to  claim 15 , wherein said first silicon oxide or oxynitride film is a silicon oxide film having a film thickness of 5 to 7 nm, said second silicon oxynitride film has a film thickness of 2 to 3 nm, and a nitrogen concentration of 1 to 3 atom %, and said third silicon oxynitride film has a film thickness of 1 to 2 nm, and a nitrogen concentration of 3 to 5 atom %.  
     
     
         17 . The method for manufacturing a semiconductor device according to  claim 6 , wherein said semiconductor substrate is a silicon substrate, the types of said dielectric films are three, and forming said three types of dielectric films comprises the steps of: 
 applying oxynitriding to a surface of said silicon substrate to form a first silicon oxynitride film so as to cover first to third regions on the surface of said silicon substrate;    forming a first silicon nitride film on said first silicon oxynitride film;    forming a first resist covering said first and third regions, and having an opening on said second region;    etching said first silicon nitride film and said first silicon oxynitride film using said first resist as a mask to remove said first silicon nitride film and said first silicon oxynitride film formed on said second region;    removing said first resist;    applying oxynitriding to the surface of said silicon substrate to form a second silicon oxynitride film with a higher film thickness and a lower nitrogen concentration than said first silicon oxynitride film on said second region;    removing said first silicon nitride film;    forming a second silicon nitride film on said first and second silicon oxynitride films;    forming a second resist covering said first and second regions, and having an opening on said third region;    etching said second silicon nitride film and said first silicon oxynitride film using said second resist as a mask to remove said second silicon nitride film and said first silicon oxynitride film formed on said third region;    removing said second resist;    applying oxidizing or oxynitriding to the surface of said silicon substrate to form a third silicon oxide or oxynitride film with a higher film thickness and a lower nitrogen concentration than said second silicon oxynitride film on said third region; and    removing said second silicon nitride film.    
     
     
         18 . The method for manufacturing a semiconductor device according to  claim 17 , wherein said first silicon oxynitride film has a film thickness of 1 to 2 nm, and a nitrogen concentration of 3 to 5 atom %, said second silicon oxynitride film has a film thickness of 2 to 3 nm, and a nitrogen concentration of 1 to 3 atom %, and said third silicon oxide or oxynitride film has a film thickness of 5 to 7 nm.  
     
     
         19 . A method for manufacturing a semiconductor device comprising the steps of: 
 forming a plurality of types of dielectric films different in film thickness from one another on a semiconductor substrate; and    applying radical nitriding to said dielectric films such that nitrogen does not reach an interface between said dielectric film with the lowest film thickness, and said semiconductor substrate to form a plurality of types of gate dielectric film.    
     
     
         20 . The method for manufacturing a semiconductor device according to  claim 19 , wherein said semiconductor substrate is a silicon substrate, and a surface layer of said silicon substrate is oxidized to form a silicon oxide film serving as said dielectric film.  
     
     
         21 . The method for manufacturing a semiconductor device according to  claim 20 , wherein said semiconductor substrate is a silicon substrate, the types of said dielectric films are three, and forming said three types of dielectric films comprises the steps of: 
 applying oxidizing to a surface of said silicon substrate to form a first silicon oxide film so as to cover first to third regions on the surface of said silicon substrate;    forming a first resist covering said first and third regions, and having an opening on said second region;    etching said first silicon oxide film using said first resist as a mask to remove said first silicon oxide film formed on said second region;    removing said first resist;    applying oxidizing to the surface of said silicon substrate to form a second silicon oxide film with a lower film thickness than said first silicon oxide film on said second region;    forming a second resist covering said first and second regions, and having an opening on said third region;    etching said first silicon oxide film using said second resist as a mask to remove said first silicon oxide film formed on said third region;    removing said second resist; and    applying oxidizing to the surface of said silicon substrate to form a third silicon oxide film with a lower film thickness than said second silicon oxide film on said third region.    
     
     
         22 . The method for manufacturing a semiconductor device according to  claim 21 , wherein said first silicon oxide film has a film thickness of 5 to 7 nm, said second silicon oxide film has a film thickness of 2 to 3 nm, and said third silicon oxide film has a film thickness of 1 to 2 nm.  
     
     
         23 . The method for manufacturing a semiconductor device according to claim  61  wherein said dielectric films consist of alumina or hafnium.  
     
     
         24 . The method for manufacturing a semiconductor device according to  claim 6 , wherein said radical nitriding comprises the steps of: 
 forming nitrogen radical in a first chamber;    introducing said nitrogen radical into a second chamber connected with said first chamber, and storing said semiconductor substrate; and    bringing said nitrogen radical in contact with said dielectric film formed on said semiconductor substrate in said second chamber.    
     
     
         25 . The method for manufacturing a semiconductor device according to  claim 24 , wherein mixed gas of helium and nitrogen, or ammonia is converted into plasma to form said nitrogen radical.