An electro-optic device, such as an LCD, includes a display unit and a peripheral drive circuit unit on a single substrate. A gate comprising a gate electrode and gate insulation film is formed on a surface of the substrate. A layer of a substance having good lattice compatibility with manocrystalline silicon is formed over the gate insulation film. A layer of monocrystalline silicon is formed over the substance layer. Manocrystalline silicon is heteroepitaxially grown by catalytic CVD or the like using a crystalline sapphire film formed on the substrate to form the monocrystalline silicon layer. The monocrystalline silican layer is used as a dual gate MOSTFT of the electro-optic device.