A semiconductor device has (a) a first conductivity type single crystal silicon carbide semiconductor substrate bearing a first conductivity type silicon carbide epitaxial layer; (b) a second conductivity type silicon carbide first semiconductor region formed on the epitaxial layer; (c) a first conductivity type silicon carbide second semiconductor region formed on the first region; (d) a first conductivity type silicon carbide third semiconductor region formed on the first region, connected to the epitaxial layer and the second region and having a higher resistance than the substrate; and (e) a gate electrode formed on an intermediate insulation layer on the third region. The third region is depleted when no voltage is applied to the gate electrode so that the device has a normally 'off' characteristic. Also claimed are similar devices in which the third region has a lower dopant concentration than the substrate and in which (i) the third region has a thickness (in the sub-micron range) such that complete depletion occurs when no voltage is applied to the gate electrode or (ii) the impurity concentration of a region of the surface channel layer, existing on the epitaxial layer surface region, is greater than that of the rest of the surface channel layer and of the epitaxial layer so that the conduction resistance is reduced.
