Low-voltage WOx gated indium-zinc-oxide thin-film transistors (TFTs) with in-plane-gate structures are fabricated by using an extremely simplified one-shadow mask method at room temperature.The proton conductive WOx solid-state electrolyte is demonstrated to form an electric-double-layer (EDL) effect associated with a huge capacitance of 0.51 μF/cm2.The special EDL capacitance of the VOx electrolyte is also extended to novel inplane-gate structure TFTs as the gate dielectric,reducing the operating voltage to 1.8 V.Such TFTs operate at n-type depletion mode with a threshold voltage of-0.5 V,saturation electron mobility of 13.2 cm2/V.s,ON/OFF ratio of 1.7 × 106,subthreshold swing of 110mV/dec,and low leakage current less than 7hA.The hysteresis window of the transfer curves is also explained by an unique reaction within the WOx electrolyte.