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We propose effective subband engineering for electron mobility enhancement on a (110) surface, utilizing uniaxial tensile strain along (110) direction. This strain causes the re-population of electrons from fourfold valleys to twofold valleys, resulting in high mobility enhancement along the (110) direction. Using this concept, a 2.0x mobility enhancement in uniaxially strained silicon-on-insulator (SOI) trigate nMOSFETs with (110) sidewall channels has been realized. Here, the uniaxial tensile strain is applied by using anisotropic strain relaxation of biaxiallv strained-SOI substrates. It is also found that (110) current (strain) direction is the best for strained trigate nMOSFETs, suggesting that optimum multigate CMOS structures with enhanced mobility of both electrons and holes can be realized on a conventional (001) wafer in the same (110) current flow direction for nMOSFETs and pMOSFETs.
Date of Publication: Feb. 2008