The bottom-gate structure ZnO based thin film transistors (ZnO-TFTs) using Bi1.5Zn1.0Nb1.5O7 (BZN) thin films as gate insulator were fabricated on Pt/SiO2/Si substrate by radio frequency magnetic sputtering at room temperature. We investigated the effect of thicknesses (100 nm, 170 nm, 250 nm, and 330 nm) of BZN thin films on the performance of BZN thin films and ZnO-TFTs. The results show that 170-nm-thick BZN thin film obtained high dielectric constant of 71, low roughness of 3.51 nm and low leakage current density of 10(-2) A/cm(2), which is approximately one order magnitude lower than that of 100-nm-thick BZN thin film. Also, we concluded that the electrical performance of ZnO-TFTs using 170-nm-thick BZN thin film as gate insulator is enhanced remarkably. On/off current ratio (1.1 x 10(5)) and field effect mobility (0.22 cm(2)/Vs) of ZnO-TFTs are approximately one order magnitude and seven times larger, respectively than that of ZnO-TFTs using 100 nm-thick BZN thin film as gate insulator. Meanwhile, surface states density (3.21 x 10(12)) of ZnO-TFTs is reduced three times. (C) 2016 Elsevier B.V. All rights reserved.