Method for fabricating semiconductor memory device

Abstract

A method for fabricating a semiconductor memory device in which a logic circuit and a nonvolatile memory are provided on a semiconductor substrate includes the steps of: forming an isolation region; forming a protective film made of an insulating material over the semiconductor substrate in a logic circuit region and a nonvolatile memory region; selectively introducing impurity ions in part of the semiconductor substrate in the logic circuit region; and removing the protective film formed over the logic circuit region. The step of introducing the impurity ions is performed before the step of removing the protective film is performed.

1 - 10 . (canceled)  
   
   
       11 . A method for fabricating a semiconductor memory device in which a logic circuit and a nonvolatile memory are provided on a semiconductor substrate, the method comprising the steps of: 
 forming a trench in the semiconductor substrate and burying an insulating film in the trench, thereby forming an isolation region;    forming a protective film made of an insulating material directly on the semiconductor substrate in a logic circuit region where the logic circuit is to be formed and a nonvolatile memory region where the nonvolatile memory is to be formed;    selectively introducing impurity ions in part of the semiconductor substrate in the logic circuit region; and    removing the protective film formed over the logic circuit region,    wherein the step of introducing the impurity ions is performed before the step of removing the protective film is performed, and    the protective film formed on the nonvolatile memory region is to serve as a trap film that accumulates charge in a memory formed in the nonvolatile memory region.    
   
   
       12 . The method of  claim 11 , wherein the protective film is made of a material having a lower etching rate with respect to hydrofluoric acid than that of the insulating film buried in the trench.  
   
   
       13 . The method of  claim 11 , wherein the protective film is made of a material having a lower etching rate with respect to a mixed solution including ammonia water and hydrogen peroxide than that of the insulating film buried in the trench.  
   
   
       14 . The method of  claim 11 , wherein the protective film is a single layer of either a silicon nitride film or a silicon oxynitride film.  
   
   
       15 . The method of  claim 11 , wherein the protective film is a multilayer film made of a plurality of insulating films including at least one of a silicon nitride film and a silicon oxynitride film.  
   
   
       16 . The method of  claim 15 , wherein the multilayer film is a stack of a silicon oxide film, either a silicon nitride film or a silicon oxynitride film, and a silicon oxide film.  
   
   
       17 . The method of  claim 15 , wherein the step of introducing the impurity ions includes a first impurity introducing step for forming a well and a second impurity introducing step for controlling a threshold voltage, and 
 the method further comprises the step of selectively removing at least one of the plurality of insulating films before the second impurity introducing step is performed.    
   
   
       18 . The method of  claim 11 , further comprising, after the step of selectively removing the protective film, the steps of: 
 forming a conductive material over the logic circuit region and the nonvolatile memory region; and    selectively etching the conductive material, thereby forming gate electrodes in the logic circuit region and the nonvolatile memory region.