Semiconductor device and method of manufacturing therefor

Abstract

An active region on a semiconductor substrate is electrically isolated by trench isolation. A structure of the trench isolation is constituted of a trench; a silicon oxide film formed on the inner wall of trench; an oxidation preventive film formed between silicon oxide film and semiconductor substrate; and a filling oxide film filling trench. Gate oxide film is formed by oxidation having a high capability by which radicals of at least one kind of hydrogen radicals and oxygen radicals are generated. Thereby, gate oxide film is formed so as to have a almost uniform thickness such that a thickness of a region directly above oxidation preventive film and a thickness of a region directly below gate electrode are almost the same is each other. According to the above procedure, there are obtained a semiconductor device having good transistor characteristics and a fabrication process therefor.

1 - 8 . (canceled) 
   
   
       9 . A semiconductor device comprising:
 a semiconductor substrate having a trench at a main surface thereof;   an oxidation preventive film including a nitrogen formed along an inner wall;   a filling layer filling said trench with said preventive film located between said filling layer and said semiconductor substrate;   a gate oxide film formed on said main surface of said semiconductor substrate and said oxidation preventive film; and   a gate electrode formed on said gate oxide film,   wherein said gate oxide film has substantially the same thickness in a region directly above said oxidation preventive film and a region directly below said gate electrode between source and drain regions, and   said gate oxide film directly above said oxidation preventive film includes said nitrogen.   
   
   
       10 . The semiconductor device according to  claim 9 , wherein said gate electrode has a floating gate electrode and a control gate, insulated from each other. 
   
   
       11 . The semiconductor device according to  claim 9 , wherein said oxidation preventive film is made from at least one of a silicon nitride film and a silicon oxynitride film.