We propose a new in-situ fluorine passivation of poly-Si TFTs using excimer laser annealing to reduce the trap state density and improve reliability significantly. To investigate the effect of an in-situ fluorine passivation, we have fabricated fluorine-passivated p-channel poly-Si TFTs and examined their electrical characteristics and stability. A new in-situ fluorine passivation brought about an improvement in electrical characteristic. Such improvement is due to the formation of stronger Si-F bonds than Si-H bonds in poly-Si channel and $SiO_2$/Poly-Si interface.