Abstract: A thin film MOS transistor has a construction which can minimize scattering of electron and thus maximize electrons mobility for allowing higher speed operation of the transistor. For this, the MOS transistor has a thin film semiconductor layer having a thickness in a range less than or equal to 100 nm, between a pair of gate electrodes which oppose each other across the semiconductor layer.

Abstract: A method of forming a thin semiconductor film has the steps of: forming a thin semiconductor film on a predetermined substrate; implanting predetermined ions in the thin semiconductor film to convert the thin semiconductor film to a thin amorphous semiconductor film; decreasing a thickness of the thin amorphous semiconductor film to a predetermined thickness; and annealing the thin amorphous semiconductor film to cause solid-phase growth. According to this method, a large thin polycrystalline semiconductor film with a crystal grain size larger than the conventional crystal grain size and a good crystal grain orientation can be uniformly formed at a low temperature. It is, therefore, possible to use such a thin semiconductor film to fabricate a thin film semiconductor device with excellent electrical characteristics.