Semiconductor device and method of manufacturing the same

Abstract

A semiconductor device comprising a semiconductor substrate having a substrate top surface on which a device is to be formed; a gate electrode electrically insulated from said semiconductor substrate by a gate-insulating film; a trench formed through said gate electrode into said semiconductor substrate to electrically isolate a device region for forming a device from the remainder region of said substrate top surface; and a boundary portion which is defined between a side surface of said trench and a bottom surface of said trench; wherein said boundary portion have spherical shapes having a curvature radius not smaller than 80 nm.

What is claimed is:  
     
         1 . A semiconductor device comprising: 
 a semiconductor substrate having a substrate top surface on which a device is to be formed;    a gate electrode formed on said substrate top surface and electrically insulated from said semiconductor substrate by a gate-insulating film;    a trench formed through said gate electrode into said semiconductor substrate to electrically isolate a device region for forming a device from the remainder region of said substrate top surface; and    a boundary portion which is defined between a side surface of said trench and a bottom surface of said trench;    wherein said boundary portion have spherical shapes having a curvature radius not smaller than 80 nm.    
     
     
         2 .The semiconductor device according to  claim 1 , further comprising an insulator filled inside said trench to electrically isolate said device region from the remainder region.  
     
     
         3 . A semiconductor device comprising: 
 a semiconductor substrate having a substrate top surface on which a device is to be formed;    a gate electrode formed on said substrate top surface and electrically insulated from said semiconductor substrate by a gate-insulating film;    a trench formed through said gate electrode into said semiconductor substrate to electrically isolate a device region for forming a device from the remainder region of the substrate top surface; and    oxide films formed on a side surface of said trench and a bottom surface of said trench, respectively;    wherein the thickness of said oxide film formed on the side surface is same as that of said oxide film formed on the bottom surface.    
     
     
         4 . The semiconductor device according to  claim 3 , further comprising a insulator filled inside said trench to electrically isolate said device region from the remainder region.  
     
     
         5 .The semiconductor device according to  claim 1 , wherein the side surface and the bottom surface of said trench are substantially planer.  
     
     
         6 .The semiconductor device according to  claim 3 , wherein the side surface and the bottom surface of said trench are substantially planer.  
     
     
         7 . A method for manufacturing a semiconductor device comprising: 
 forming a gate-insulating film on a semiconductor substrate;    forming a gate electrode on said gate-insulating film to be electrically insulated from said semiconductor substrate;    etching said gate electrode, said gate insulting film and said semiconductor substrate to form a trench which is used to electrically isolate a device region for forming a device from the remainder region on the substrate top surface; and    etching the inside of said trench using a gas containing Cl 2  or HBr.    
     
     
         8 . The method according to  claim 7 , further comprising after etching said trench using a gas containing Cl 2  or HBr: 
 oxidizing the inside of said trench in a hydrogen H 2  and oxygen O 2  atmosphere.    
     
     
         9 . The method according to  claim 7 , further comprising after etching said trench using a gas containing Cl 2  or HBr: 
 oxidizing the inside of said trench in an ozone O 3  atmosphere.    
     
     
         10 . The method according to  claim 8 , further comprising: 
 filling an insulator inside said trench to electrically isolate said device region from the remainder region.    
     
     
         11 . The method according to  claim 9 , further comprising: 
 filling an insulator inside said trench to electrically isolate said device region from the remainder region.