| 摘要 |
PROBLEM TO BE SOLVED: To keep a holding voltage low by forming a second lightly doped P-type semiconductor substrate with further lower concentration between lightly doped N-type and lightly doped P-type semiconductor regions. SOLUTION: A lightly doped N-type semiconductor region 17 is formed by partially etching a P-type silicon substrate, embedding an oxide, forming a device isolation region 15, and implanting ions. Thereafter, a lightly doped P-type semiconductor region 16 is formed, and part of an area on the region 17 and part of an area on the region 16 are opened, and a P-type impurity is ion-implanted onto the surface of the substrate at a high concentration in a substantially vertical direction, thereby forming a heavily doped P-type semiconductor region 19 and an anode 20. An N-type impurity such as arsenic is ion-implanted onto the surface of the substrate at a high concentration in a substantially vertical direction, thereby forming a heavily doped N-type semiconductor region 23 and a cathode 22. Since a lightly doped P-type semiconductor substrate is interposed between the regions 17 and 16, a holding voltage at an ON state can be made low.
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