A method of forming a polycrystalline silicon active layer for use in a thin film transistor is provided. The method includes forming a buffer layer over a substrate, forming an amorphous silicon layer over the buffer layer, applying a catalytic metal to a surface of the amorphous silicon layer, crystallizing the amorphous silicon layer having the catalytic metal thereon into a polycrystalline silicon layer, annealing the polycrystalline silicon layer in an N.sub.2 gas atmosphere to stabilize the polycrystalline silicon layer, etching a surface of the polycrystalline silicon layer using an etchant, and patterning the polycrystalline silicon layer to form an island-shaped active layer.