| 摘要 |
An active pixel sensor which provides reduced dark current, improved sensitivity, and improved modulation transfer function. An N well, surrounded by a P well is formed in a P type epitaxial substrate. A P + region is formed extending from within the P well into the substrate leaving a gap between the P + region and the N well. A gate dielectric is formed covering at least the gap, part of the P + region, and part of the N well. A gate electrode is formed on the gate dielectric over the gap, part of the P + region, and part of the N well. The gate electrode is biased so that the region of the substrate under the gate electrode is accumulated with holes and the region of the N well under the gate electrode is depleted of electrons. This will reduce the dark current and improve the sensitivity of the active pixel sensor. In a second embodiment the P type epitaxial substrate is replaced by an N type epitaxial substrate, the N well is replaced by a P well, N + regions are replaced by P + regions, and P + regions are replaced by N + regions. In this second embodiment the gate electrode is biased so that the region of the substrate under the gate electrode is depleted of electrons and the region of the P well under the gate electrode is accumulated with holes.
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