Functional gate metal-oxide-semiconductor field-effect transistors using tunnel injection/ejection of trap charges enabling self-adjustable threshold voltage for ultra low power operation

摘要

Metal-oxide-semiconductor field-effect transistors (MOSFETs) with a functional gate, which enables self-adjustment of threshold voltage (Vlh), were proposed for ultralow power operation and fabricated with conventional complementary metal-oxide-semiconductor (CMOS) technology. In the on-current state of fabricated nMOSFETs, electron ejection from the charge trap layer by direct tunneling makes Vth low and increases on-current further. In the off-current state, electron injection into the charge trap layer makes Vth high and suppresses subthreshold leakage current. Although the characteristic time of electron transfer of the functional gate from on-current state to off-current state is fairly long, the logic mode operating principle has been verified with the experimental device. Reduction of tunnel oxide thickness (T_(ox)) will reduce the time, which will lead to the practical use of the proposed device for CMOS logic application.