Hole mobility enhancement in MOS-gated Ge/sub x/Si/sub 1-x//Si heterostructure inversion layers

Effective hole mobility enhancements of 50% at room temperature and over 100% at 90 K, compared to all-Si controlled devices, are demonstrated by placing a buried epitaxial Ge/sub x/Si/sub 1-x/ layer 7.5 to 10.0 nm beneath the gate oxide of a PMOS transistor. Mobility degradation caused by misfit dislocations in the inversion region is seen in structures with GeSi/sub 1-x/ layers that exceed the equilibrium critical thickness.>