A method for fabricating a low temperature polysilicon thin film transistor incorporating a multi-layer channel passivation stack, and for activating dopant ions in a polysilicon gate in the TFT structure has been described. In the method, a multi-layer channel passivation stack consisting of a first insulating material layer, a metal layer and a second insulating material layer are first deposited on a polysilicon gate to shield a channel region in the gate during a laser irradiation process for activating the dopant ions in the gate. Any damages to the channel region of the polysilicon gate by the laser irradiation or the rapid thermal annealing step can be avoided, as well as the dopant impurity out-diffusion and lateral diffusion problems.