| 摘要 |
PURPOSE:To obtain a guard ring having breakdown strength difference sufficient against a light-receiving section by a method wherein an impurity is introduced selectively into a predetermined region in a base body, heat treatment is executed under the state, in which a mask with a prescribed opening is formed, and the introduced impurity is diffused externally and diffused to the base body through the mask again. CONSTITUTION:A specified insulating film 7 is shaped to an epitaxial-wafer for an avalanche-photodiode (APD), a ring-shaped opening 8 is bored, and Mg ions are implanted to form an ion introducing layer 9. The insulating film 7 is removed, and an insulating film (a second mask) 10 is deposited and shaped again. When the whole is thermally treated in an atmosphere adjusted so as to prevent the dissociation of the constituent of the wafer, one part of Mg in the ion implanting layer 9 is diffused externally into the atmosphere from an opening 11 once, and diffused to the wafer from the opening 11 again, thus shaping a p-type guard ring 12 having extension in the transverse direction. Accordingly, the guard ring having large breakdown strength difference against a main junction can be acquired.
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