A 3D, vertically stacked silicon nanowire (SiNW) field effect transistor (FET) featuring a high density array (7×20) of fully depleted channels has been successfully fabricated by a CMOS compatible process on silicon on insulator (SOI) and functionalized for streptavidin detection for the first time. The channels are surrounded by conformal high-κ gate dielectrics (HfO2), and their conductivity can be uniquely tuned by three gates; a backgate (BG) and two symmetrical Pt side gates (SG) through a liquid, offering unique sensitivity tuning with high gate coupling (SS=75 mV/dec, α'=SS60mV/dec/SSmeasured=0.8, with highest sensitivity=93-99%, obtained for I=1 0pA-10nA, in weak inversion) ever published. © 2013 IEEE.