| 摘要 |
PURPOSE:To eliminate the variability of withstanding voltage between a gate and a cathode by a method wherein, after a plurality of opposite conductivity type regions are formed on one surface of a semiconductor substrate by diffusion, the regions are etched except the bottom parts which are used as gate regions and cathode regions are provided on the parts of the substrate protruding between the gate regions. CONSTITUTION:A plurality of P<+> type regions 6 are formed in an N<-> type Si substrate 5 with intervals by diffusion. With insulating films 7 formed on the surfaces of the substrate 5 between the regions 6, the regions 6 are removed by etching except the bottom parts which are used as gate regions 10. Then apertures 9 are formed in the films 7 on the protruding surfaces of the substrate 5 and the films 7 are covered with doped polycrystalline silicon films 12. The impurity in the silicon films 12 is diffused by a heat treatment to form N<+> type regions 11 which are used as cathode regions on the protruding surfaces of the substrate 5. After that, the previously used silicon films 12 are again utilized as cathode electrodes 12. With this constitution, the distance between the gate and the cathode along the vertical direction can be defined so that the yield can be improved.
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