Enhanced hole mobilities in surface-channel strained-Si p-MOSFETs

The strain dependence of the hole mobility in surface-channel p-MOSFETs employing pseudomorphic, strained-Si layers is reported for the first time. The hole mobility enhancement is observed to increase roughly linearly with the strain as the Ge content in the relaxed Si/sub 1-x/Ge/sub x/ buffer layer increases. When compared to the device with x=0.1, the devices with x=0.22 and 0.29 exhibit hole mobility enhancement factors of 1.4 and 1.8, respectively. In spite of the high fixed charge in our gate oxides, the device with Ge content x=0.29 still exhibits a mobility 1.3 times that of bulk Si MOSFETs with state-of-the-art oxides. The first measurements of the transconductance enhancements in submicron strained-Si p-MOSFETs are also reported.