Patent ID: 7247583

Claim:
A method for manufacturing a strained silicon wafer, comprising: a first step of preparing a single crystal silicon substrate; a second step of forming a graded SiGe layer on the single crystal silicon substrate under temperature ranging from 800° C. to 1100° C., the graded SiGe layer comprising a first Ge composition ratio progressively increased stepwisely from 5 to 60% atomic ratio; a third step of forming a SiGe constant composition layer on the graded SiGe layer, the SiGe constant composition layer comprising a Ge composition ratio substantially equal to Ge composition ratio a surface of the graded SiGe layer which is adjacent to the SiGe constant composition layer; and a fourth step of forming a strained Si layer comprising a thickness less than 15 nm on the SiGe constant composition layer, wherein the second through fourth steps are performed under reduced pressure atmosphere while the single crystal silicon substrate is rotated in a circumferential direction at a rate of 300 rpm to 1500 rpm.