A novel solid-phase crystallization method is suggested for synthesizing large-grained polycrystalline silicon (poly-Si) films at low temperature (similar to 500 degrees C) and in a short time (1 h). Hydrogenated microcrystalline-silicon (mu c-Si:H) and hydrogenated amorphous-silicon (a-Si:H) layers are sequentially deposited on a glass substrate in order to form a-Si:H/mu c-Si:H bilayers before annealing through conventional furnace heating and a new annealing method, plasma heating, respectively. It is found that the crystallization rate of the bilayers during the plasma heating is much higher than that of the bilayers during the furnace heating. Moreover, the crystallization reaction is enhanced more effectively during the annealing in the case of the bilayers which are hydrogen-plasma treated between the depositions of mu c-Si:H and a-Si:H layers than in the case of those which are not. Finally, poly-Si films with grains of similar to 0.4 mu m are obtained through the plasma heating method combined with the hydrogen-plasma treatment.