A semiconductor device according to an embodiment may include a board, an insulation layer disposed on the board, a threshold voltage control layer disposed on the insulation layer, a first semiconductor layer disposed on the threshold voltage control layer, and a second semiconductor layer disposed on the threshold voltage control layer to cover a portion of the first semiconductor layer. A negative differential resistance device according to an embodiment has an advantageous effect in that the gate voltage enables a peak voltage to be freely controlled within an operation range of the device by forming the threshold voltage control layer.