The strong correlation between the microstructural characteristics of ZnO channel layers grown at various temperatures by radio-frequency magnetron sputtering and the electrical performances of resulting bottom-gate thin film transistors (TFTs) was reported. Transmission electron microscopy revealed that increasing growth temperature enhanced degree of c-axis preferred orientation and enlarged width of columns in the ZnO films. The ZnO channel layers grown at 250 and 350 degrees C exhibited TFT saturation behavior. However, growing them at >= 350 degrees C produced small grains in the junctions of ZnO/SiO(2) interface and grain boundaries, which led to hump behavior in TFT transfer curve caused by formation of additional boundaries. (C) 2011 Elsevier B.V. All rights reserved.