We present experimental results on on-current and transconductance gain and mobility enhancement in Si nanowire FETs (NW-FETs) fabricated on silicon-on-insulator (SOI) and biaxially tensile strained SOI (SSOI). The Si NW-FETs show very high I-on/I-off-ratios of 10(7) and off-currents as low as 10(-13) A. Inverse sub-threshold slopes of about 80 mV/dec for SOI n- and p-FETs and 65 mV/dec for strained SOI n-FETs were obtained. The on-current and transconductance of Si NW-nFETs fabricated on strained SOI substrates are 2.5 and 2.1 times larger, respectively, compared to identical devices on SOI due to uniaxial tensile strain along the wires. An electron mobility enhancement by a factor of 2.3 in uniaxial tensile strained NW-FETs was found. Moreover, the on-currents of n- and p-NW-FET are more symmetrical compared to planar devices, differing only by a factor of 1.6, for < 110 > NW channel direction on a (100) wafer. (C) 2009 Elsevier Ltd. All rights reserved.