Patent ID: 7425751
Filing Date: 2008-09-16
Classification: H01L

Abstract:
1. A strained silicon-on-SiGe semiconductor device comprising: graded composition SiGe layer over a semiconductor substrate; uniform composition SiGe buffer layer over said graded composition SiGe layer; a strained silicon layer over said uniform composition SiGe buffer layer; isolation shallow trench extending into said strained-silicon and SiGe buffer layers; silicon dioxide encroachment structure under said strained-silicon layer, having width dimension of said shallow trench in said strained-silicon layer being smaller than the width dimension of said shallow trench in said SiGe buffer layer; source/drain structure which has larger width in said strained silicon layer than its width in said uniform composition SiGe buffer layer; and the encroachment structure located so as to butt against and not underneath the source and drain regions, extending into said uniform composition SiGe buffer layer; and device elements comprising gate and said source/drain regions.