Semiconductor memory device and method for manufacturing semiconductor device

Abstract

After a lower silicon oxide film is formed on a silicon region, a silicon film is formed on the lower silicon oxide film by, for example, a thermal CVD method. Subsequently, the silicon film is completely nitrided by a plasma nitriding method to be replaced by a silicon nitride film. Subsequently, a surface layer of the silicon nitride film is oxidized by a plasma oxidizing method to be replaced by an upper silicon oxide film. An ONO film as a multilayered insulating film composed of the lower silicon oxide film, the silicon nitride film, and the upper silicon oxide film is formed.

1 . A method for manufacturing a semiconductor device, comprising: 
 a step of forming a lower silicon oxide film;    a step of forming a silicon nitride film on the lower silicon oxide film by a CVD method; and    a step of oxidizing a surface of the silicon nitride film by a plasma oxidizing method, wherein    a multilayered insulating film composed of the lower silicon oxide film, the silicon nitride film and an upper silicon oxide film is formed.    
     
     
         2 . The method for manufacturing the semiconductor device according to  claim 1 , wherein 
 the silicon nitride film is a charge-storage film of a memory cell.    
     
     
         3 . The method for manufacturing the semiconductor device according to  claim 1 , wherein 
 the multilayered insulating film is formed as a dielectric film provided between a floating gate and a control gate in the memory cell.    
     
     
         4 . The method for manufacturing the semiconductor device according to  claim 1 , wherein 
 a gate insulation film is formed in a peripheral circuit region by the plasma oxidizing method simultaneously with the upper silicon oxide film.    
     
     
         5 . The method for manufacturing the semiconductor device according to  claim 1 , wherein 
 a film thickness of the silicon nitride film formed by the CVD method is 5 nm or above.    
     
     
         6 . The method for manufacturing the semiconductor device according to  claim 1 , wherein 
 the silicon nitride film is formed by conducting nitriding processing in which plasma is excited by microwave in an atmosphere of a source gas containing nitrogen to generate a nitrogen radical.    
     
     
         7 . The method for manufacturing the semiconductor device according to  claim 6 , wherein 
 the source gas does not contain hydrogen.    
     
     
         8 . The method for manufacturing the semiconductor device according to  claim 1 , wherein 
 the upper silicon oxide film is formed by conducting oxidizing processing in which plasma is excited by microwave in an atmosphere of a source gas containing oxygen to generate an oxygen radical.    
     
     
         9 . The method for manufacturing the semiconductor device according to  claim 8 , wherein 
 the source gas does not contain hydrogen.    
     
     
         10 . A semiconductor memory device, comprising: 
 a memory cell; including    a semiconductor substrate,    an insulation film including a silicon nitride film having a charge-capture function, formed on the semiconductor substrate,    a gate electrode formed on the semiconductor substrate via the insulation film, and    a pair of impurity diffused layers formed on the semiconductor substrate, wherein    the silicon nitride film is a uniform and dense nitrided film formed by only plasma nitriding through microwave excitation or a series of processing including the plasma nitriding.    
     
     
         11 . The semiconductor memory device according to  claim 10 , wherein 
 the insulation film is a multilayered insulating film composed of a silicon nitride film on a lower silicon oxide film.    
     
     
         12 . The semiconductor memory device according to  claim 10 , wherein 
 the insulation film is a multilayered insulating film composed of the lower silicon oxide film, the silicon nitride film, and an upper silicon oxide film.    
     
     
         13 . The semiconductor memory device according to  claim 11 , wherein 
 either or both of the lower silicon oxide film and/or the upper silicon oxide film is/are (a) uniform and dense oxide film(s) formed by plasma oxidization through microwave excitation.    
     
     
         14 . The semiconductor memory device according to  claim 13 , wherein 
 a gate insulation film of a transistor as a component of a peripheral circuit is a uniform and dense oxide film formed by plasma oxidization through microwave excitation, and simultaneously formed with the upper silicon oxide film.    
     
     
         15 . A semiconductor memory device, comprising: 
 a semiconductor substrate;    a gate insulation film formed on said semiconductor substrate;    an island-shaped floating gate having a charge-capture function, the charge-capture function being formed on said semiconductor substrate via said insulation film;    a dielectric film formed on said floating gate;    a control gate formed on said floating gate via said dielectric film; and    a pair of impurity diffused layers formed on said semiconductor substrate, wherein    said dielectric film includes a uniform and dense silicon nitride film formed by only plasma nitriding through microwave excitation or a series of processing including the plasma nitriding.    
     
     
         16 . The semiconductor memory device according to  claim 15 , wherein 
 said dielectric film is a multilayered insulating film composed of the silicon nitride film formed on a lower silicon oxide film.    
     
     
         17 . The semiconductor memory device according to  claim 15 , wherein 
 said dielectric film is a multilayered insulating film composed of the lower silicon oxide film, the silicon nitride film, and an upper silicon oxide film.    
     
     
         18 . The semiconductor memory device according to  claim 16 , wherein 
 either or both of the lower silicon oxide film and/or the upper silicon oxide film is/are (a) uniform and dense oxide film(s) formed by plasma oxidization through microwave excitation.