A systematic study of the noise performances of polycrystalline silicon (polysilicon) thin-film transistors (TFTs) made by excimer laser crystallization is presented. The drain current spectral density of these devices shows an evident1/fbehavior and the origin of the noise was attributed to carrier number fluctuations. The flat-band voltage spectral density was found to be strongly correlated with the field-effect mobility, suggesting that the microscopic mechanism causing the carrier number fluctuations involves the localized states present at the grain boundaries. The noise level in the devices with the best electrical characteristics is comparable with that observed inc-Si metal–oxide–semiconductor field effect transistors, a major improvement if compared to polysilicon TFTs made by solid-phase crystallization. ©1997 American Institute of Physics.