| 摘要 |
PROBLEM TO BE SOLVED: To protect an element in a semiconductor device without occupying a large area of protective circuit on a chip. SOLUTION: An interval 12a, between a first N-type embedded diffused layer 2 and a second N-type diffused layer 3 formed on the surface of a P-type semiconductor substrate 1, is adjusted so that the fluctuations of a punch-through voltage becomes smaller according to the impurity concentration of the substrate 1. When the voltage applied across electrodes 11 and 10 becomes higher and a depletion layer reaches a second N-type embedded diffused layer 3, punch- through occurs, and the voltage and current characteristics between the electrodes 10 and 11 become a clamping characteristic such as the reverse breakdown characteristic of a P-N junction diode, and the diode is energized and protects an element to be protected.
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