Semiconductor device having contact plug formed in double structure by using epitaxial stack and metal layer and method for fabricating the same

Abstract

Disclosed are a contact plug of a semiconductor device and a method for fabricating the same. The semiconductor device includes: an epitaxial stack formed by inserting a heteroepitaxy layer between a pair of homoepitaxy layers; and a contact plug including a metal layer on the epitaxial stack. Accordingly, in accordance with the present invention, the contact plug is selectively doped in a high concentration, thereby reducing a contact resistance. Furthermore, the present invention also provides an effect of reducing degradation in a device property without decreasing yields of products by minimizing a thermal budget through using a SEG-silicon germanium layer capable of obtaining a high doping concentration and a high deposition speed.

1 . A semiconductor device, comprising:
 an epitaxial stack formed by inserting a heteroepitaxy layer between a pair of homoepitaxy layers; and   a contact plug including a metal layer on the epitaxial stack.   
   
   
       2 . The semiconductor device of  claim 1 , wherein the epitaxial stack is formed by stacking a first SEG (selective epitaxy growth)-silicon layer, a SEG-silicon germanium layer and a second SEG-silicon layer through a SEG process. 
   
   
       3 . The semiconductor device of  claim 2 , wherein the first SEG-silicon layer, the SEG-silicon germanium layer and the second SEG-silicon layer are doped with phosphorous (P). 
   
   
       4 . The semiconductor device of  claim 3 , wherein a doping concentration of P ranges from approximately 1×10 19  atoms/cm 3  to approximately 5×10 19  atoms/cm 3  for the first and the second SEG-silicon layers and a doping concentration of P ranges from approximately 8×10 19  atoms/cm 3  to approximately 1×10 20  atoms/cm 3  for the SEG-silicon germanium layer. 
   
   
       5 . The semiconductor device of  claim 2 , wherein a thickness of the first and the second SEG-silicon layers ranges from approximately 10 Å to approximately 50 Å and a thickness of the SEG-silicon germanium layer ranges from approximately 100 Å to approximately 300 Å. 
   
   
       6 . The semiconductor device of  claim 5 , the SEG-silicon germanium layer includes a germanium (Ge) content ratio ranging from approximately 5% to approximately 30%. 
   
   
       7 . The semiconductor device of  claim 1 , wherein the metal layer is formed with use of one selected from a group consisting of titanium (Ti), titanium nitride (TiN), nickel (Ni), tungsten (W) and cobalt (Co). 
   
   
       8 - 19 . (canceled)