A semiconductor device comprises at least a semiconductor layer including source and drain areas of a first conductive type and of a high impurity concentration and a channel area positioned between the source and drain areas, an insulation layer covering at least the channel area, and a gate electrode positioned close to the insulation layer. The channel area at least comprises a first channel area of a low resistance, positioned close to the insulation layer and having a second conductive type opposite to the first conductive type, and a second channel area of a high resistance, having the first conductive type and positioned adjacent to the first channel area.