The island-shaped semiconductor films 4603 a and 4603 b can be provided by forming an amorphous semiconductor film, which is formed of a material including silicon (Si) as a main component (for example, SixGe1-x, or the like) and the like, by using a sputtering method, an LPCVD method, a plasma CVD method, or the like over the insulating film 4602 which is formed in advance over the substrate 4601