Methods for manufacturing a semiconductor device include forming a seed layer containing a silicon material on a substrate. An amorphous silicon layer containing amorphous silicon material is formed on the seed layer. The amorphous silicon layer is doped with an impurity. A laser beam is irradiated onto the amorphous silicon layer to produce a phase change of the amorphous silicon layer and change the amorphous silicon layer into a single-crystal silicon layer based on the seed layer.