Abstract: A monocrystalline semiconductor film is formed on an insulating film first by selectively forming at least one insulating film which has sides substantially perpendicular to <100> or <211>-axes, contiguous to a cubic crystal system monocrystalline semiconductor substrate. An amorphous film of a cubic crystal system semiconductor material is formed to cover an exposed surface of substrate and the insulating film. The amorphous semiconductor film is annealed under a condition such that the amorphous film is grown from the substrate by solid-phase epitaxial growth, thereby converting the amorphous film to a monocrystalline semiconductor film having a crystal lattice continuous to that of the substrate.

Abstract: Processes for forming a wafer having SOS structure are provided. A single crystal silicon layer is formed on a principal plane of a sapphire substrate. An amorphous portion is formed in a silicon layer leaving its surface portion of predetermined depth as it is and by injecting Si.sup.+ into the single crystal silicon layer. This amorphous portion reaches the interface of sapphire substrate. A wafer thus formed is placed on a cooling table in a furnace. The substrate is fixedly bonded onto the cooling table with indium and cooled to a predetermined temperature. A temperature higher than that applied to the sapphire substrate is applied to the silicon layer including the amorphous portion using a heater arranged in the furnace and N.sub.2 gas flowing into the furnace. The SOS wafer is then returned to room temperature.