Patent ID: 7663189

Claim:
A semiconductor device formed on a sapphire substrate, comprising: a silicon layer at most one-tenth of a micrometer (0.1 μm) thick having opposite first and second surfaces, the second surface on and having an interface with the sapphire substrate, the silicon layer doped with an impurity of a first conductive type; a source region in the silicon layer, doped with an impurity of a second conductive type; a gate electrode formed above part of the silicon layer; a first diffusion layer in the silicon layer, extending into a first area beneath the gate electrode, having a diffusion depth less than the thickness of the silicon layer, doped with an impurity of the second conductive type but having a lower impurity concentration than the source region; and a first high-concentration diffusion layer in the silicon layer between and in contact with both the first diffusion layer and said interface, and doped with an impurity of the first conductive type but having a higher impurity concentration than in the silicon layer under the gate electrode, the first high-concentration diffusion layer separated away from the first surface of the silicon layer.