A MISFET having extremely high mobility comprising a first silicon layer (Si layer)(12), a silicon layer containing carbon (Si 1-y C y layer)(13) and an optional, second silicon layer (Si layer)(14) stacked in this order on a silicon substrate (10). The carbon content and thickness of the Si 1-y C y layer acting as a channel layer of the MISFET are such that said Si 1-y C y layer is under tensile strain whereby the conduction and valence bands thereof are split. Therefore, charge carriers having a smaller effective mass, which have been induced by an electric field applied to an insulated gate electrode (15,16), are confined in the Si 1-y C y layer, and move in the channel direction. Furthermore, if the silicon layer containing carbon is made of Si 1-x-y Ge x C y , a structure suitable for a high-performance CMOS device can be formed. Alternatively, the silicon layers may contain a slight amount of carbon or germanium, and a Schottky gate may be provided whereby a MESFET is achieved.