Abstract: An n-type diffusion layer, an insulating layer and a first aluminum electrode are formed on a p-type silicon substrate. Fe.sup.2+ (divalent Fe) having a vacant orbit not filled with an electron is implanted into a region of the insulating layer to form an impurity atom layer. A second aluminum electrode is formed which is in contact with the n-type diffusion layer. A voltage that increases the potential of the first aluminum electrode is applied between the first and second aluminum electrodes. The voltage is increased. In this situation, when the fermi level of the n-type diffusion layer and an impurity level which is the energy level for filling the vacant orbit of the Fe.sup.2+ are matched, a resonance tunnelling current flows. Thereafter, when there is a change to the state of non-resonance state, a negative-resistance characteristic is exhibited in which the current decreases as the voltage is increased.