Semiconductor device having a spacer layer doped with slower diffusing atoms than substrate

Abstract

A semiconductor device includes a silicon substrate heavily-doped with phosphorous. A spacer layer is disposed over the substrate and is doped with dopant atoms having a diffusion coefficient in the spacer layer material that is less than the diffusion coefficient of phosphorous in silicon. An epitaxial layer is also disposed over the substrate. A device layer is disposed over the substrate, and over the epitaxial and spacer layers.

1 . A method of fabricating a semiconductor device on a silicon substrate, said silicon substrate heavily-doped with phosphorous atoms, said method comprising: 
 forming a spacer layer over said substrate;    doping said spacer layer with dopant atoms having a diffusion coefficient in said spacer layer that is less than a diffusion coefficient of phosphorous in silicon;    forming an epitaxial layer over said substrate; and    forming an active layer over said substrate.    
   
   
       2 . The method of  claim 1 , wherein said dopant atoms include at least one of arsenic and antimony.  
   
   
       3 . The method of  claim 1 , wherein said forming and doping processes occur in a substantially simultaneous manner.  
   
   
       4 . The method of  claim 1 , wherein said forming a spacer layer comprises epitaxially grown silicon.  
   
   
       5 . The method of  claim 1 , wherein said spacer layer is formed directly upon said substrate, and said epitaxial layer is disposed over said spacer layer, and said active area is disposed over said epitaxial layer.  
   
   
       6 . A method of reducing diffusion of phosphorous atoms from a silicon substrate heavily-doped with phosphorous atoms to a device layer of a semiconductor device, said method comprising: 
 forming a spacer layer over said substrate; and    doping said spacer layer with dopant atoms having a diffusion coefficient in said spacer layer that is less than a diffusion coefficient of phosphorous in silicon.    
   
   
       7 . The method of reducing diffusion of  claim 6 , further comprising the process of forming an epitaxial layer over said spacer layer.  
   
   
       8 . The method of  claim 6 , wherein said spacer layer comprises epitaxial silicon and said dopant atoms include at least one of arsenic and antimony.  
   
   
       9 . The method of  claim 6 , wherein said forming and doping processes occur in a substantially simultaneous manner,