A micromachine includes a microstructure and a semiconductor element formed over one insulating substrate. The micromachine includes including a movable layer containing polycrystalline silicon and a space below or above the layer. Such polycrystalline silicon is formed on an insulating surface, so that it is used as a microstructure and used for forming a semiconductor element. Accordingly, a semiconductor device may include a microstructure and a semiconductor element provided over one insulating substrate.