Finfet transistor structure and method for making the same

Abstract

A FINFET transistor structure includes a substrate, a fin structure, an insulating layer and a gate structure. The fin structure is disposed on the substrate and directly connected to the substrate. Besides, the fin structure includes a fin conductive layer and a bottle neck. The insulating layer covers the substrate and has a protruding side which is formed by partially surrounding the bottle neck of the fin structure, and a bottom side in direct contact with the substrate so that the protruding side extend to and under the fin structure. The gate structure partially surrounds the fin structure.

What is claimed is: 
     
         1 . A FINFET transistor structure, comprising:
 a substrate;   an insulating layer covering said substrate and having a top side and a bottom side in direct contact with said substrate, wherein at least one of said top side and said bottom side is uneven;   a fin structure disposed on said insulating layer and comprising a fin conductive layer and a source/drain; and   a gate structure partially surrounding said fin structure.   
     
     
         2 . The FINFET transistor structure of  claim 1 , wherein said insulating layer comprises a plurality of U-shape bottoms so that said fin structure is disposed between adjacent said U-shape bottoms. 
     
     
         3 . The FINFET transistor structure of  claim 1 , further comprising:
 a cap layer covering said fin conductive layer.   
     
     
         4 . The FINFET transistor structure of  claim 1 , wherein said cap layer comprises an oxynitride. 
     
     
         5 . The FINFET transistor structure of  claim 1 , wherein said fin structure comprises a rounded corner. 
     
     
         6 . The FINFET transistor structure of  claim 1 , wherein said insulating layer is substantially stress free. 
     
     
         7 . A FINFET transistor structure, comprising:
 a substrate;   a fin structure disposed on said substrate and directly connected to said substrate, wherein said fin structure comprises a fin conductive layer and a bottle neck;   an insulating layer covering said substrate and having a protruding side which is formed by partially surrounding said bottle neck of said fin structure and a bottom side in direct contact with said substrate, wherein said protruding side extends to and under said fin structure; and   a gate structure partially surrounding said fin structure.   
     
     
         8 . The FINFET transistor structure of  claim 7 , further comprising:
 a cap layer covering said fin conductive layer.   
     
     
         9 . The FINFET transistor structure of  claim 7 , further comprising:
 a shallow trench isolation disposed under said insulating layer and having a top side in direct contact with said insulating layer, wherein said bottom side is larger than said top side.   
     
     
         10 . The FINFET transistor structure of  claim 8 , wherein said cap layer comprises an oxynitride. 
     
     
         11 . The FINFET transistor structure of  claim 7 , wherein said fin structure comprises a rounded corner. 
     
     
         12 . The FINFET transistor structure of  claim 7 , wherein said insulating layer is substantially stress free. 
     
     
         13 . The FINFET transistor structure of  claim 7 , further comprising:
 a pad layer disposed between said shallow trench isolation and said insulating layer as well as said substrate and said fin structure.   
     
     
         14 . The FINFET transistor structure of  claim 7 , wherein said bottle neck has a width between 3 μm-10 μm. 
     
     
         15 . The FINFET transistor structure of  claim 7 , wherein a width of said bottle neck is 40%-60% of that of said fin structure.