Semiconductor Device Having a Random Grained Polysilicon Layer and a Method for its Manufacture

Abstract

A semiconductor device having a random grained polysilicon layer and a method for its manufacture are provided. In one example, the device includes a semiconductor substrate and an insulator layer on the substrate. A first polysilicon layer having a random grained structure is positioned above the insulator layer, a semiconductor alloy layer is positioned above the first polysilicon layer, and a second polysilicon layer is positioned above the semiconductor alloy layer.

1 . A semiconductor device comprising:
 a semiconductor substrate;   an insulator layer on the substrate;   a first polysilicon layer positioned above the insulator layer, wherein the first polysilicon layer has a random grained structure;   a second polysilicon layer positioned above the first polysilicon layer; and   a semiconductor alloy layer positioned between the first and second polysilicon layers.   
   
   
       2 . The device of  claim 1  wherein the insulator layer is a silicon dioxide layer having a thickness between about 17 and 35 Angstroms. 
   
   
       3 . The device of  claim 1  wherein the first polysilicon layer has a thickness between about 50 and 300 Angstroms. 
   
   
       4 . The device of  claim 1  wherein the first polysilicon layer is doped. 
   
   
       5 . The device of  claim 1  wherein a grain size of the first polysilicon layer is between about 6 and 7 nanometers. 
   
   
       6 . The device of  claim 1  wherein the alloy layer comprises Si (1-x) Ge x , 
   
   
       7 . The device of  claim 6  wherein the content (x) of germanium, described as mole fraction, is between about 2 and 8. 
   
   
       8 . The device of  claim 1  wherein the alloy layer has a thickness between about 500 and 1000 Angstroms. 
   
   
       9 . The device of  claim 1  wherein the alloy layer is doped. 
   
   
       10 . The device of  claim 1  wherein the second polysilicon layer comprises a random grained polysilicon. 
   
   
       11 . The device of  claim 1  wherein the second polysilicon layer comprises a columnar grained polysilicon.