We report, for the first time, the use of a single step deposition of semiconductor channel layer to simultaneously achieve both n- and p-type transport in transparent oxide thin film transistors (TFTs). This effect is achieved by controlling the concentration of hydroxyl groups (OH-groups) in the underlying gate dielectrics. The semiconducting tin oxide layer was deposited at room temperature, and the maximum device fabrication temperature was 350 °C. Both n and p-type TFTs showed fairly comparable performance. A functional CMOS inverter was fabricated using this novel scheme, indicating the potential use of our approach for various practical applications.