Sol-gel derived Zn1- xZrxO films and thin-film transistors (TFTs) were investigated in this study, where x ranges from 0.00 to 0.10. The effects of the Zr additive on the crystallinity, grain size, and surface morphology of Zn1- xZrxO films are discussed. Zn1- xZrxO-TFTs exhibited much lower off-state current (I-OFF) and higher on/off ratio than pure ZnO-TFT. The behavior of I-OFF related to the carrier concentration (n) of Zn1-xZrxO films and the correlation between n and the grain size are interpreted. The optimized I-OFF and on/off ratio of Zn1- xZrxO-TFT were 3.24 x 10(-13) A/mu m and 8.89 x 10(6) where x = 0.03, respectively. (c) 2006 The Electrochemical Society.