| 摘要 |
A solid-state image pickup device includes a semiconductor substrate of a first conductivity type, and a photoelectric cell, including an impurity region of a second conductivity type formed on the semiconductor substrate, to produce a signal charge corresponding to the quantity of incident light at a first junction surface between the impurity region of the second conductivity type and the semiconductor substrate. The device further includes an impurity region of the first conductivity type formed on the semiconductor substrate to effect isolation between the impurity regions of the second conductivity type, and a charge transfer unit for transferring the signal charge produced in the photoelectric cell. This device is characterized in that the impurity concentration of the impurity region of the second conductivity type is high in the vicinity of at least a portion of a second junction surface between the impurity region of the second conductivity type and the impurity region of the first conductivity type, and is low in a range spaced from the second junction surface. With the device thus configured, under a greatly reverse-biased condition due to charge transportation, the high concentration portion of the impurity region of the second conductivity type is depleted, and under a small reverse-biased condition at the time of the charge accumulation, the high concentration portion is placed in a non-depleted condition. This permits the junction capacity at the time of the charge accumulation to be large, thus enabling realization of a solid-state image pickup device having less afterimage.
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