| 摘要 |
PROBLEM TO BE SOLVED: To ensure sufficient block breakdown voltage at a high temperature or high current injection by providing a lightly doped n-type semiconductor layer having impurity concentration lower than a specified level between an n-type substrate and a first p-type semiconductor layer. SOLUTION: An active layer is formed on an n-type substrate 1 and then a first p-type semiconductor layer 7, an n-type semiconductor layer 8 and a second p-type semiconductor layer 9 are formed sequentially on the opposite sides of the active layer. A lightly doped n-type semiconductor layer 2 having impurity concentration of 3×1017 cm-3 or below is provided between the n-type substrate 1 and the first p-type semiconductor layer 7. Consequently, injection of electrons into the first p-type semiconductor layer 7 can be suppressed. Since the number of electrons advancing through the first p-type semiconductor layer 7 and charging up the n-type semiconductor layer 8 is decreased, breakdown voltage of a thyristor is enhanced at the high current injection or high temperature.
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