Method of fabricating semiconductor device with shallow trench isolation

Abstract

In fabrication of a semiconductor device, a first insulating film, electrode film and silicon nitride film sequentially stacked on a semiconductor substrate are etched with the substrate so that a trench is formed. The electrode film is then exposed. A second insulating film buried in the trench is isotropically etched so that an upper side wall of the electrode film is exposed, so that a side end of an upper surface of the insulating film is located between the upper surfaces of the substrate and electrode film and so that a middle upper portion of an upper surface of the second insulating film is higher than the side end and lower than the upper surface of the first electrode film, A third insulating film is formed on the upper surface of the first electrode film so as to entirely cover the upper surface of the second insulating film.

1 . A method of fabricating a semiconductor device comprising: 
 sequentially stacking a first insulating film, a first electrode film and a silicon nitride film on a first upper surface of a semiconductor substrate;    etching the silicon nitride film, the first electrode film, the first insulating and the semiconductor substrate to form a trench;    burying a second insulating film in the trench;    planarizing a second upper surface of the second insulating film using the silicon nitride film as a stopper;    removing the silicon nitride film to expose a third upper surface of the first electrode film;    isotropically etching the second insulating film so that an upper side wall of the first electrode film is exposed, so that a side end portion of a fourth upper surface of the second insulating film is located between the first and the third upper surfaces and so that a middle upper portion of the fourth upper surface of the second insulating film is higher than the side end portion and is lower than the third upper surface relative to the first upper surface;    forming a third insulating film on the third upper surface, the upper side wall and the fourth upper surface; and    forming a second electrode film on the second insulating film, wherein the fourth upper surface is entirely covered by the second insulating film.    
   
   
       2 . The method according to  claim 1 , wherein the etching step includes a wet etching process.  
   
   
       3 . The method according to  claim 2 , wherein the wet etching process includes etching with a solution including a buffered hydrofluoric acid (BHF).  
   
   
       4 . A method of fabricating a semiconductor device, comprising: 
 sequentially stacking a first insulating film, a first electrode film and a silicon nitride film on a first upper surface of a semiconductor substrate;    etching the silicon nitride film, the first electrode film, the first insulating film and the semiconductor substrate to form a trench;    forming a silicon oxide film on a side surface of the first electrode film exposed in the trench;    burying a second insulating film in the trench;    planarizing a second upper surface of the second insulating film using the silicon nitride film as a stopper;    removing the silicon nitride film to expose a third upper surface of the first electrode film so that the second upper surface protrudes from the third upper surface;    isotropically etching an upper portion of the second insulating film so that an upper side wall of the first electrode film is exposed, a side end portion of a fourth upper surface of the second insulating film is located between the first and the third upper surfaces, and a middle upper portion of the fourth upper surface of the second insulating film is higher than the side end portion and is lower than the third upper surface relative to the first upper surface;    anisotropically etching the second insulating film, so that the silicon oxide film is exposed;    forming a third insulating film on the third upper surface, the upper side wall, the silicon oxide film and the fourth upper surface; and    forming a second electrode film on the second insulating film, wherein the fourth upper surface is entirely covered by the second insulating film.    
   
   
       5 . The method according to  claim 4 , wherein the etching step includes a wet etching process.  
   
   
       6 . The method according to  claim 5 , wherein the wet etching process includes etching with a solution including a buffered hydrofluoric acid (BHF).