Insulating buffer film and high dielectric constant semiconductor device and method for fabricating the same

Abstract

A semiconductor device includes: an n-transistor including a first gate insulating film made of a high-dielectric-constant material and a first gate electrode fully silicided with a metal, the first gate insulating film and the first gate electrode being formed in this order over a semiconductor region; and a p-transistor including a second gate insulating film made of the high-dielectric-constant material and a second gate electrode fully silicided with the metal, the second gate insulating film and the second gate electrode being formed in this order over the semiconductor region. If the metal has a work function larger than a Fermi level in potential energy of electrons of silicon, a metal concentration of the second gate electrode is higher than that of the first gate electrode whereas if the metal has a work function smaller than the Fermi level of silicon, a metal concentration of the second gate electrode is lower than that of the first gate electrode.

1 - 48 . (canceled) 
     
     
         49 . A method for fabricating a semiconductor device, the method comprising steps of:
 forming on a semiconductor region an n-transistor including a first gate insulating film and a first gate electrode made of silicon and a p-transistor including a second gate insulating film and a second gate electrode made of silicon;   selectively removing the second gate electrode of the p-transistor;   selectively forming a third gate electrode for the p-transistor from which the second gate electrode has been removed, the third gate electrode being made of a first conductive film containing a first metal;   selectively removing the first gate electrode of the n-transistor; and   selectively forming a fourth gate electrode for the n-transistor from which the first gate electrode has been removed, the fourth gate electrode being made of a second conductive film containing a second metal.   
     
     
         50 . The method of  claim 49 , wherein the first metal or the second metal contains nickel or platinum as a main component. 
     
     
         51 . The method of  claim 49 , wherein each of the first and second gate insulating films is made of a high-dielectric-constant material. 
     
     
         52 . The method of  claim 51 , wherein the high-dielectric-constant material contains at least one metal selected from the group consisting of silicon, germanium, hafnium, zirconium, titanium, tantalum, aluminum and a rare-earth metal. 
     
     
         53 . The method of  claim 51 , wherein in the step of forming the n-transistor and the p-transistor, a buffer film is formed between the first gate insulating film and the first gate electrode and between the second gate insulating film and the second gate electrode. 
     
     
         54 . The method of  claim 53 , wherein the buffer film includes nitrogen, titanium, or aluminum. 
     
     
         55 . The method of  claim 53 , wherein the step of forming the n-transistor and the p-transistor includes, before formation of the buffer film, a step of performing heat treatment on the first gate insulating film made of the high-dielectric-constant material and the second gate insulating film made of the high-dielectric-constant material.