A fabrication process is provided for semiconductor devices having a crystalline semiconductor film formed on a substrate, the semiconductor film being an active layer of a transistor and being mainly composed of silicon, and includes at least an underlevel protection layer fabrication step of forming a silicon oxide film as an underlevel protection layer on the substrate; a first processing step of forming a semiconductor film, which is mainly composed of silicon, on the underlevel protection layer; and a second processing step of irradiating a pulsed laser light on the semiconductor film. The semiconductor film is irradiated by a pulsed laser, the wavelength of the pulsed laser light is between 370 and 710 nm. As a result, using a low temperature process, high performance thin film semiconductor devices can be produced simply and reliably.