| 摘要 |
An image sensor having a plurality of photodetectors and a source follower, storing photo-charges generated by the photodetectors in gate of a MOS transistor and outputting voltage signals converted from the photo-charges, integrally formed on a single semiconductor substrate. The source follower is configured with p-channel MOS transistors to restrain generation of stray carrier. Further, the p-channel MOS transistor of the source follower on the power source side is formed on an n-type well whose impurity concentration is higher than that of an n-type semiconductor substrate where the p-channel MOS transistor on the ground side is formed. In this configuration, the absolute value of the threshold voltage of the p-channel MOS transistor on the ground side becomes lower than that of the p-channel MOS transistor on the power source side, thus gain of the source follower is increased.
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