Low voltage oxide thin-lm transistors (TFTs) operating below 1.0 V were developed using a high dielectric constant tantalum oxide produced by thermal oxidation. Thermal oxidation was carried out at 400, 500, and 600 °C under an oxygen atmosphere. The tantalum oxide was evaluated by X-ray photoelectron spectroscopy (XPS). XPS con rmed the binding energy of Ta4f, indicating the binding state of tantalum oxide. The bottom gate oxide TFT with the gate insulator of tantalum oxide grown at 500 °C exhibited mobility of 12.61 cm2/V and a threshold voltage of 0.46 V. The transfer characteristics at the drain voltages below 1.0 V show its applicability to low voltage operation below 1 V. The bootstrapped inverter with developed oxide TFTs operated well at the operation voltages of both the 1.0 and 2.0 V.