Semiconductor device and fabrication method thereof

Abstract

A semiconductor device includes a substrate having at least two fins thereon and an isolation trench between the at least two fins; and an isolation structure in the isolation trench. The isolation structure consists of a liner layer covering a lower sidewall of each of the at least two fins and a bottom surface of the isolation trench, and a stress-buffer film on the liner layer. The stress-buffer film is a silicon suboxide film of formula SiOy, wherein y<2.

What is claimed is: 
     
         1 . A semiconductor device, comprising:
 a substrate having at least two fins thereon and a first isolation trench between the at least two fins, wherein the first isolation trench is disposed within a first region; and   a first isolation structure in the first isolation trench, wherein the first isolation structure consists of a liner layer covering a lower sidewall of each of the at least two fins and a bottom surface of the first isolation trench, and a stress-buffer film on the liner layer, wherein the stress-buffer film is a silicon suboxide film of formula SiOy, wherein y<2.   
     
     
         2 . The semiconductor device of  claim 1  further comprising:
 a second isolation trench in the substrate within a second region; and 
 a second isolation structure in the second isolation trench, wherein the second isolation structure comprising the liner layer, the stress-buffer film, and a trench-fill oxide layer on the stress-buffer film. 
 
     
     
         3 . The semiconductor device of  claim 2 , wherein the first region is a dense region and the second region is an isolated region. 
     
     
         4 . The semiconductor device of  claim 2 , wherein a width of the second isolation trench is greater than that of the first isolation trench. 
     
     
         5 . The semiconductor device of  claim 2 , wherein the liner layer is a silicon dioxide layer. 
     
     
         6 . The semiconductor device of  claim 2 , wherein the trench-fill oxide layer may be a silicon oxide film of formula SiOx, wherein x<y. 
     
     
         7 . The semiconductor device of  claim 1 , wherein a lower portion of the first isolation trench does not include the trench-fill oxide layer. 
     
     
         8 . The semiconductor device of  claim 7 , wherein the lower portion is located at least below half of a trench depth of the first isolation trench within the first region. 
     
     
         9 . The semiconductor device of  claim 1 , wherein the stress-buffer film has a thickness that is greater than or equal to about 40 angstroms at a fin pitch of about 48 nm. 
     
     
         10 . The semiconductor device of  claim 1 , wherein the stress-buffer film has a thickness ranging between about 40 angstroms and about 80 angstroms at a fin pitch of about 48 nm.