Polycrystalline silicon thin film transistors (poly-Si TFTs) with the ion implantation of fluorine elements were investigated in this study. The electrical performance and reliability were reported comprehensively. Experimental work has shown the electrical characteristics of excimer laser crystallized F-ions-implanted poly-Si TFTs are improved effectively, especially for field effect mobility. It is also found that the fluorine piled up at the poly-Si interface during thermal annealing, for the TFT fabricated without a prior deposition of pad oxide. The stronger Si-F bonds replace the Si-Si/Si-H, leading to the superior electrical reliability. However, the dose of F ions is critical in poly-Si, or the electrical characteristics of TFT devices will be degraded. (c) 2007 Published by Elsevier B.V.