Graded high germanium compound films for strained semiconductor devices

Abstract

Embodiments of an apparatus and methods for providing a graded high germanium compound region are generally described herein. Other embodiments may be described and claimed.

1 . A strained semiconductor device, comprising:
 a gate electrode on at least two gates of a multi-gate channel region;   a graded high germanium content film stack, comprising:
 a low germanium content bottom layer; 
 a transition layer, comprising germanium, directly adjacent to the low germanium content bottom layer, wherein the transition layer transitions from a low germanium content, at an interface with the low germanium content bottom layer, to a high germanium content; and 
 a high germanium content layer directly adjacent to the transition layer; and 
   wherein the graded high germanium content film stack is configured to strain the multi-gate channel region of the strained semiconductor device.   
     
     
         2 . The device of  claim 1 , further comprising a spacer formed directly adjacent to the gate electrode. 
     
     
         3 . The device of  claim 2 , wherein the graded high germanium content film stack is positioned directly adjacent to the multi-gate channel region and the spacer. 
     
     
         4 . The device of  claim 1 , wherein a lower portion of the transition layer has a germanium content ranging between 20-25 atomic weight % and an upper portion of the transition layer has a germanium content ranging between 40-55 atomic weight %. 
     
     
         5 . The device of  claim 1 , wherein the low germanium content bottom layer is doped with boron. 
     
     
         6 . The device of  claim 1 , wherein the multi-gate channel region is directly adjacent to the gate electrode, the graded high germanium content film stack, and the substrate. 
     
     
         7 . A transistor comprising:
 a gate stack and spacers on three gates of a tri-gate channel region, wherein the spacers are formed on laterally opposite sides of the gate stack; and   a graded high germanium content film stack directly adjacent to the tri-gate channel region.   
     
     
         8 . The transistor of  claim 7 , wherein the graded high germanium content film is formed of a silicon-germanium seed layer, a transition layer, and a high germanium content layer. 
     
     
         9 . The transistor of  claim 8 , wherein the graded high germanium content film stack is directly adjacent to the tri-gate channel region and the spacers. 
     
     
         10 . The transistor of  claim 9 , wherein the graded high germanium content film stack recessed within at least one of the spacers. 
     
     
         11 . The transistor of  claim 8 , wherein the graded high germanium content film stack is doped with boron. 
     
     
         12 . The transistor of  claim 8 , wherein the tri-gate channel region is directly adjacent to a substrate and the gate stack is formed directly adjacent to the substrate and the three gates of a tri-gate channel region. 
     
     
         13 . The transistor of  claim 8 , wherein the gate stack comprises a workfunction metal layer. 
     
     
         14 . A multi-gate semiconductor device, comprising:
 a gate stack directly adjacent to a substrate and two or more gates of a multi-gate channel region;   spacers formed on laterally opposite sides of the gate stack; and   a source region and a drain region directly adjacent the substrate and the multi-gate channel region, the source region and the drain region comprising a silicon-germanium bottom layer, a transition layer, and a high germanium content layer.   
     
     
         15 . The device of  claim 14 , wherein a lower portion of the transition layer has a germanium content ranging between 20-25 atomic weight % and an upper portion of the transition layer has a germanium content ranging between 40-55 atomic weight %. 
     
     
         16 . The device of  claim 14 , wherein the silicon-germanium bottom layer is doped with boron to a concentration ranging between 5.0×10 19  atoms/cm 3  to 1.5×10 20  atoms/cm 3 . 
     
     
         17 . The device of  claim 15 , wherein the high germanium content layer is doped with boron to a concentration ranging between 2.0×10 20  atoms/cm 3  to 3.0×10 20  atoms/cm 3 . 
     
     
         18 . The device of  claim 15 , wherein a thickness of the transition layer is selected from a range between 150 Å and 450 Å. 
     
     
         19 . The device of  claim 18 , wherein a thickness of the silicon-germanium bottom layer is selected from a range between 100 Å-300 Å. 
     
     
         20 . The device of  claim 19 , wherein a thickness of the high germanium content layer is selected from a range between 300 Å-600 Å.