The fabrication and characterization of strained-Si material grown on a relaxed Si0.79 Ge0.21/graded Si1-x- Gex/Si virtual substrate, using reduced pressure chemical vapor deposition, are presented. The Ge concentration of the constant composition SiGe layer and the grading rate of the graded SiGe layer are estimated with double-crystal X-ray diffraction and further confirmed by SIMS measurements. The surface root mean square roughness of the strained Si cap layer is 2.36nm,and the strain is about 0.83% as determined by atomic force microscopy and Raman spectra, respectively. The threading dislocation density is on the order of 4 × 10^4cm^-2. Furthermore, it is found that the stress in the strained Si cap layer is maintained even after the high thermal budget process, nMOSFET devices are fabricated and measured in strained-Si and unstrained bulk-Si channels. Compared to the co-processed bulk-Si MOSFETs at room temperature,a significant low vertical field mobility enhancement of about 85% is observed in the strained-Si devices.
