A thin semiconductor film is crystallized in a high yield by being irradiated with laser light. An insulating film, a semiconductor film, an insulating film, and a semiconductor film are stacked in this order over a substrate. Laser light irradiation is performed from above the substrate to melt the semiconductor films of a lower layer and an upper layer, whereby the semiconductor film of the lower layer is crystallized. With the laser light irradiation, the semiconductor film of the upper layer changes to a liquid state, thereby reflecting the laser light and preventing the semiconductor film of the lower layer from being overheated with the laser light. Further, by melting the semiconductor film of the upper layer as well, time for melting the semiconductor film of the lower layer can be extended.