Fully-depleted Strained-Si on Insulator NMOSFETs without Relaxed SiGe Buffers

Fully-depleted strained Si n-channel MOSFETs were demonstrated on a compliant borophosphorosilicate insulator (BPSG) without an underlying SiGe buffer layer. Stress balance of a SiGe/Si structure, transferred onto BPSG by wafer bonding and Smart-cut® processes, is utilized for the first time to make strained-Si on insulator (sSOI) by a process that does not involve the introduction of misfit dislocations. Strained-Si n-channel MOSFETs with a strain level of 0.6%, equivalent to that of a conventional strained Si layer grown on a relaxed Si _0.85Ge _0.15 buffer, exhibit 60% mobility enhancement over the control, in good agreement with theory. This approach to fabricating strained Si overcomes any potential process or device complexity due to the presence of a SiGe layer in the final devices.