Thermal crystallization of amorphous silicon films deposited on glass substrates, using conventional and rapid thermal processing have been investigated for the realization of polycrystalline thin film transistors (TFTs). The films annealed by these two methods exhibit a similar structure. Measurements of the drain current in the off state and the field effect mobility for various channel film thicknesses show that the rapid thermal annealing (RTA) crystallization technique leads to TFTs with an electrical behavior as good as the one obtained by conventional annealing.