It is an object of the present invention to provide a micro-electro-mechanical-device having a microstructure and a semiconductor element over one surface. In particular, it is an object of the present invention to provide a method for simplifying the process of forming the microstructure and the semiconductor element over one surface. A space in which the microstructure is moved, that is, a movable space for the microstructure is formed by processing an insulating layer which is formed in a process of forming the semiconductor element. The movable space can be formed by forming the insulating layer having a plurality of openings and making the openings face each other to be overlapped each other.