Indium gallium oxide-based thin-film transistors (TFTs) are formed using rf magnetron sputtering of the channel layer. These TFTs exhibit qualitatively ideal characteristics, including excellent drain current saturation. Various deposition parameters, annealing treatments, and stoichiometries are explored. Varying the oxygen partial pressure is found to have a significant effect on device performance. Decreasing the oxygen partial pressure increases the incremental channel mobility μinc while decreasing (becomes more negative) the turn-on voltage Von. Increasing indium concentration of the channel material increases μinc, while decreasing Von. The maximum value of μinc, ∼ 27 cm² V-¹ s-¹, is obtained by annealing at 600 °C, with corresponding Von and drain current on-to-off ratio values of approximately −14 V and >10⁶, respectively. Additionally, TFTs subjected to a 200 °C postdeposition annealing exhibit μinc and Von of ∼ 19 cm² V-¹ s-¹ and 2 V, respectively.