| 摘要 |
PROBLEM TO BE SOLVED: To prevent a low voltage Zener diode from deteriorating in ESD strength due to reduction in impurity concentration of the outermost surface (with a depth of about 0 to 1μm) of a guard ring, a leakage current from increasing due to the formation of an inversion layer, and the Zener diode from deteriorating in product characteristics, such as Zener breakdown voltage. SOLUTION: After a guard ring is oxidized and pushed into or a main junction is oxidized and pushed into, the same conductivity impurities with the guard ring are diffused into a solid phase or a vapor phase or implanted as ions for doping, by which a high concentration (1.0×1020 to 1.0×1022/cm3) impurity doped layer is formed on the outermost surface layer 5 (with a depth of about 0 to 1μm) of the guard ring to make up for a reduction in the impurity concentration of an outermost surface layer 8 due to thermal history in processes which are carried out after the thermal treatment where a guard ring is oxidized and pushed in, and a low-voltage Zener diode of high ESD strength and low coupling capacitance can be stably manufactured.
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