Semiconductor device

Abstract

A semiconductor device comprises: a memory cell region having a first transistor and a peripheral circuit region having a second transistor. The first transistor has a first source electrode and a first drain electrode, a first buried gate insulating film which is formed along an inner wall of a trench and whose relative dielectric constant is higher than a relative dielectric constant of silicon oxide, and a buried gate electrode. The second transistor has a second source electrode and a second drain electrode, a first on-substrate gate insulating film whose relative dielectric constant is higher than a relative dielectric constant of silicon oxide, and an on-substrate gate electrode. A first Hf content percentage, which is a content percentage of hafnium in the first buried gate insulating film, is different from a second Hf content percentage, which is a content percentage of hafnium in the first on-substrate gate insulating film.

What is claimed is: 
     
         1 . A semiconductor device, comprising:
 a memory cell region having a first transistor, and a peripheral circuit region which is formed around said memory cell region and has a second transistor, on a semiconductor substrate, wherein said first transistor comprises:
 a first source electrode and a first drain electrode which are formed on said semiconductor substrate, 
 a first buried gate insulating film which is formed along an inner wall of a trench formed in said semiconductor substrate between said first source electrode and said first drain electrode and whose relative dielectric constant is higher than a relative dielectric constant of silicon oxide, and 
 a buried gate electrode which is formed in said trench on said first buried gate insulating film, comprises metal and functions as a word line; and 
   wherein the said second transistor comprises:
 a second source electrode and a second drain electrode which are formed on said semiconductor substrate, 
 a first on-substrate gate insulating film which is formed on a surface of said semiconductor substrate between said second source electrode and said second drain electrode and whose relative dielectric constant is higher than a relative dielectric constant of silicon oxide, and 
 an on-substrate gate electrode which is formed on said first on-substrate gate insulating film and comprises metal; 
   said first buried gate insulating film and said first on-substrate gate insulating film comprising a compound containing a metal element,   wherein a first metal content percentage, which is a content percentage of the metal element in said first buried gate insulating film, is different from a second metal content percentage, which is a content percentage of the metal element in said first on-substrate gate insulating film.   
     
     
         2 . The semiconductor device according to  claim 1 , wherein said first metal content percentage is lower than said second metal content percentage. 
     
     
         3 . The semiconductor device according to  claim 1 , wherein said first metal content percentage is lower than said second metal content percentage by 10 atm % or more. 
     
     
         4 . The semiconductor device according to  claim 1 , wherein said compound in said first buried gate insulating film is not crystallized even if said first buried gate insulating film is heat-treated at a temperature of 700 degrees Celsius or more. 
     
     
         5 . The semiconductor device according to  claim 1 , wherein said first metal content percentage is 10 atm % to 90 atm %. 
     
     
         6 . The semiconductor device according to  claim 1 , wherein said first buried gate insulating film comprises hafnium silicate. 
     
     
         7 . The semiconductor device according to  claim 1 , wherein said first buried gate insulating film has a thickness ranging from 1 nm to 3.5 nm. 
     
     
         8 . The semiconductor device according to  claim 1 , further comprising:
 a second buried gate insulating film between an inner wall of said trench of said semiconductor substrate and said first buried gate insulating film.   
     
     
         9 . The semiconductor device according to  claim 8 , wherein said second buried gate insulating film comprises a silicon oxide film or a silicon oxynitride film. 
     
     
         10 . The semiconductor device according to  claim 1 , wherein a part of said second transistors in said peripheral circuit region further has/have a second on-substrate gate insulating film having higher relative dielectric constant than that of silicon oxide on said first on-substrate gate insulating film. 
     
     
         11 . The semiconductor device according to  claim 10 , wherein said second on-substrate gate insulating film comprises alumina. 
     
     
         12 . The semiconductor device according to  claim 1 , wherein said second transistor further has a third on-substrate insulating film between said semiconductor substrate and said first on-substrate insulating film. 
     
     
         13 . The semiconductor device according to  claim 12 , wherein said third on-substrate insulating film is a silicon oxide film or a silicon oxynitride film. 
     
     
         14 . The semiconductor device according to  claim 1 , further comprising:
 a cap buried insulating film which is buried in said trench of said semiconductor substrate on said buried gate electrode.   
     
     
         15 . The semiconductor device according to  claim 1 , wherein said first on-substrate gate insulating film is formed above a most upper surface of said semiconductor substrate. 
     
     
         16 . The semiconductor device according to  claim 1 , wherein said first on-substrate gate insulating film comprises hafnium oxide or hafnium silicate. 
     
     
         17 . A semiconductor device, comprising:
 a first transistor and a second transistor on a semiconductor substrate, wherein said first transistor comprises:
 a first gate insulating film which is formed along an inner wall of a trench formed in said semiconductor substrate and whose relative dielectric constant is higher than a relative dielectric constant of silicon oxide, and 
 a first gate electrode which is buried in said trench and formed on said first gate insulating film, and comprises metal; and 
   wherein said second transistor comprises:
 a second gate insulating film which is formed on a most upper surface of said semiconductor substrate and whose relative dielectric constant is higher than a relative dielectric constant of silicon oxide, and 
 a second gate electrode which is formed on said second gate insulating film and comprises metal; 
   said first gate insulating film and said second gate insulating film comprising a compound containing a metal element, wherein a first metal content percentage, which is a content percentage of the metal element in said first gate insulating film, is different from a second metal content percentage, which is a content percentage of the metal element in said second gate insulating film.   
     
     
         18 . The semiconductor device according to  claim 17 , wherein said first metal content percentage is lower than said second metal content percentage. 
     
     
         19 . The semiconductor device according to  claim 17 , wherein said first metal content percentage is lower than said second metal content percentage by 10 atm % or more. 
     
     
         20 . The semiconductor device according to  claim 17 , wherein said first metal content percentage is 10 atm % to 90 atm %.