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The drain-current enhancement of the mechanically strained strained-Si NMOSFET device is investigated for the first time. The improvements of the drain current are found to be 3 4% and 6 5% for the strained-Si and control Si devices, respectively, with the channel length of 25 m at the external biaxial tensile strain of 0.037%, while the drain-current enhancements are 2 0% and 4 5% for strained-Si and control Si devices, respectively, with the channel length of 0.6 m. Beside the strain caused by lattice mismatch, the mechanical strain can further enhance the current drive of the strained-Si NMOSFET. The strain distribution due to the mechanical stress has different effect on the current enhancement depending on the strain magnitude and channel direction. The smaller current enhancement for strained-Si device as compared to the control device can be explained by the saturation of mobility enhancement at large strain.Index Terms-Drain-current enhancement, mechanical strain, strained-Si nMOSFET.

We demonstrate enhancement of electron mobility in nMOSFET using an ultrathin pure Ge crystal channel layer directly grown on a bulk Si wafer. A thin Si crystal layer is also grown on top of a Ge crystal channel layer as a capping layer. Using the Si/Ge/Si structure, a maximum 2.2X enhancement in electron mobility is achieved while good gate dielectric properties and junction qualities of bulk Si devices are maintained.

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