<p>A semiconductor device whose spike voltage generated in turn-off operation is suppressed, comprising a first region of a first conductor; a second region of a second conductor formed on the first region; a third region of the first conductor formed on the second region; and a fourth region of the second conductor formed on the third region. The second region has a depletion-layer-formation assisting layer with a short life-time formed near the third region; a tail-current suppressing layer with a shorter life-time than the depletion-layer-formation assisting layer formed near the first region; and depletion-layer-formation suppressing layer with a longer life-time than the depletion-layer-formation assisting layer formed in between the depletion-layer-formation assisting layer and the tail-current suppressing layer.</p>
