In this work we report dense arrays of accumulation-mode gate-all-around Si nanowire nMOSFETs with sub-5 nm cross-sections in a highly doped regime. The integration of local stressor technologies (both local oxidation and metal-gate strain) to achieve ⩾2.5 GPa uniaxial tensile stress in the Si nanowire is reported. The deeply scaled Si nanowire including such uniaxial tensile stress shows a low-field electron mobility of 332 cm2/V s at room temperature, 32% higher than bulk mobility at the equivalent high channel doping. The conduction mechanism as well as high temperature performance was studied based on the electrical characteristics from room temperature up to ≈400 K and a VTH drift of −1.72 mV/K and an ionized impurity scattering-based mobility reduction were observed.