| 摘要 |
A buried oxide is provided in a substrate of a photodiode so as to be opposed to a cathode and is in contact with a lower end of a depletion layer. The buried oxide is polarized owing to charges forming the depletion layer and thus works as a capacitor. A capacitor formed in the depletion layer and the additional capacitor made by the buried oxide are, therefore, connected in series, which reduces a total junction capacitance Cs. Increase in photo-detection voltage Vs results in according to an equation, Vs=Qp/Ct, since an amount of photocharge Qp is constant. The increase in the photo-detection voltage Vs allows an improvement in the SN ratio of the photodiode. Further, easy formation of the buried oxide, for example, by implanting oxygen ions, permits low-cost manufacturing of the photodiode.
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