A high performance ultralow temperature polycrystalline silicon (poly-Si) thin film transistor (TFT) was obtained on a flexible metal foil substrate using the optimization of a benzocyclobutene (BCB) planarization process for a rough flexible metal foil substrate surfaces, the high quality SiO2 interface layer formation between the gate dielectric film and the poly-Si film using plasma oxidation, and a successful crystallization of large grain poly-Si films with a sequential lateral solidification (SLS) method. High performances with field effect mobilities of 196 and 95 cm2 V-1 s-1, threshold voltages of 1.6 and -1.5 V and sub-threshold swings of 0.53 and 0.45 V/decade were obtained for n-channel metal–oxide–semiconductor (nMOS) and p-channel metal–oxide–semiconductor (pMOS) TFT on flexible metal foil substrate, respectively.