In conventional TFTs, SiO(2) or SiN(x) have been used as gate insulators But they could not induce the high on-current due to their low-capacitance Since they have low-capacitance that originated from low dielectric constant, on-current of TFTs with low-k insulated are limited by low-capacitance We have investigated high-k materials, such as HfO(2), ZrO(2) and modified structures for the use of gate insulators in oxide thin film transistors ZrO(2) and HfO(2) are the most attractive materials with their superior properties, such as high breakdown field intensity (similar to 15 MV/cm), high dielectric constant (similar to 25), and the capability of room-temperature process Since they have high-capacitance due to high dielectric constant, it can be easily expected to result in high on-current In this work, we demonstrated the comparison of oxide thin film transistors with HfO(2), ZrO(2) and SiO(2) and the roles of gate insulators are analyzed In the result, oxide thin film transistors with SiO(2), HfO(2) and ZrO(2) have on-currents of similar to 100 mu A, similar to 500 mu A, and similar to 3 mA, respectively Especially oxide thin film transistor with ZrO(2) has larger on-current than oxide thin film transistor with HfO(2) The result means that ZrO(2) is more suitable than HfO(2) for the gate-dielectric material which can be fabricated at room temperature (C) 2009 Elsevier B V. All rights reserved