In this letter, we have developed a high-k Tb2O3 gate dielectric polycrystalline silicon (poly-Si) thin-film transistors (TFTs) prepared under a CF4 plasma treatment. A high-performance TFT device that has a low threshold voltage of 0.89 V, a high effective carrier mobility of 59.6 cm2/V s, a small subthreshold swing of 212 mV/dec, and a high ION/IOFF current ratio of 8.15×106 can be achieved. This phenomenon is attributed to fluorine atoms into poly-Si films can effectively passivate the trap states near the Tb2O3/poly-Si interface. The fluorine incorporation also enhanced electrical reliability of the Tb2O3 poly-Si TFT. All of these results suggest that the CF4 plasma-treated poly-Si Tb2O3 TFT is a good candidate for high-performance TFTs.