Ex parte YOSHIDA et al. - Page 11

          Appeal No. 95-1555                                                          
          Application 07/871,530                                                      

               To answer this question, we first must determine what the              
          prior art places before the skilled artisan in his workshop.                
          Anderson teaches in column 1, lines 39-47, that for DRAMs of the            
          trench capacitor type, engineers have observed a problem in which           
          leakage current flows through the upper portion of the storage              
          node near the top of the trench into the silicon substrate.                 
          Anderson states in column 1, lines 48-51, that it is the object             
          of their invention to provide a process which will eliminate                
          undesirable leakage current near the top of the trench for trench           
          capacitor type high density dynamic random access memories.                 
          Anderson further teaches in column 1, lines 57-68, a method of              
          reducing gate diode leakage in trench type capacitor type dynamic           
          random access memory devices.  Anderson teaches that the storage            
          node of the capacitor is formed by placing a storage node                   
          material, such as arsenic, into the trench walls of the device at           
          a first tilt and a second tilt.  The angle of the second tilt is            
          higher than the angle of the first tilt.  This higher angle                 
          provides the storage node with a larger concentration of doping             
          around the upper portion of the trench walls.  This larger                  
          concentration of doping reduces the charge leaking for the upper            
          portion of the storage node into the substrate of the                       
          semiconductor material.                                                     


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