Films of zinc tin oxide (ZTO), grown from solutions with zinc acetate dehydrate and tin(II) 2-ethylhexanoate dissolved in 2-methoxyethanol, have been used to fabricate thin-film transistors in combination with solution-processed aluminum oxide as the gate insulator. And the nonhomogeneity of the single-layer ZTO films, caused by both ZTO film-substrate interaction and surface crystallization, has been studied, which is essential to achieve high performance transistors. In the bottom-contact thin-film transistor based on a Sn-rich layer of ZTO, a high mobility of 78.9 cm(2) V-1 s(-1) in the saturation region has been obtained, with an on-to-off current ratio of 10(5) and a threshold gate voltage of 1.6 V.