Bottom-gate thin film transistors with amorphous zinc tin oxide channels were grown by atomic layer deposition. The films maintained their amorphous character up to temperatures over 500 °C. The highest field effect mobility was ∼13 cm2/V·s with on-to-off ratios of drain current ∼109–1010. The lowest subthreshold swing of 0.27 V/decade was observed with thermal oxide as a gate insulator. The channel layers grown at 170 °C showed better transistor properties than those grown at 120 °C. Channels with higher zinc to tin ratio (∼3–4) also performed better than ones with lower ratios (∼1–3).