We fabricated a Top contact Pentacene based Organic thin-film transistor (OTFTs) with bi-layer TiO₂/Au electrodes. The performance of the devices after inserting TiO₂ layer between organic layer and Au electrode is highly improved. On comparing with pentacene based transistor with only Au electrode, the hole injection was largely enhanced and the highest field-effect mobility is increased from 0.37 cm²/ (Vs) to 0.63 cm²/ (Vs) in the device with bilayer TiO₂/Au electrodes. We also measured the temperature dependence characteristics and surface morphology of both the devices. Both the devices showed strong temperature dependence. We observed that the barrier height is tremendously decreased after inserting a thin layer of TiO₂ between the organic layer and Au electrodes. The improved device performance was due to the decreased barrier height and decrease in the surface roughness of pentacene after inserting a suitable metal oxide layer between the pentacene and the Au electrodes. Our experimental results clearly show that the insertion of metal oxide between Au electrode and pentacene layer is an effective way to improve the performance of the pentacene based organic thin-film transistor (OTFTs).