FETs including a gated oxide semiconductor spacer interfacing with a channel semiconductor. Transistors may incorporate a non-oxide channel semiconductor, and one or more oxide semiconductors disposed proximal to the transistor gate electrode and the source/drain semiconductor, or source/drain contact metal. In advantageous embodiments, the oxide semiconductor is to be gated by a voltage applied to the gate electrode (i.e., gate voltage) so as to switch the oxide semiconductor between insulating and semiconducting states in conjunction with gating the transistor's non-oxide channel semiconductor between on and off states.