Fully CMOS compatible Silicon-nanowire (SiNW) Gate-All-Around (GAA) n- and p-MOS transistors are fabricated with nanowire channel in different crystal orientations and characterized at various temperatures down to 5K. SiNW width is controlled in 1 nm steps and varied from 3 to 6 nm. Devices show high drive current (2.4 mA/μm for n-FET, 1.3 mA/μm for p-FET), excellent gate control, and reduced sensitivity to temperature. Strong evidences of carrier confinement are noticed in term of Id-V8 oscillations and shift in threshold voltage with SiNW diameter. Orientation impact has been investigated as well.