The disclosed MOS transistor includes a channel region formed of a lightly doped semiconductor layer disposed in a surface portion of a heavily doped semiconductor layer subsequently disposed on a lightly doped semiconductor substrate. The channel region may be of the identical or opposite conductivity type to the heavily doped semiconductor layer that has the same type conductivity as the substrate. Also the channel region may be of an intrinsic semiconductive material. A source and a drain region may be disposed in the lightly or highly doped layer. Alternatively the source and drain regions may reach the substrate.