Pixel structure of a solid-state image sensor employing a charge sorting method

A pixel structure of a solid-state image sensor employing a charge sorting method that distributes electrons generated by photoelectric conversion to perform charge storage, said structure comprising:

• a substrate;
• a photodiode in said substrate that generates electrons by photoelectric conversion;
• a plurality of charge-storage sections that store electrons generated in said photodiode;
• and
• a gate structure on said substrate
• that is arranged between said photodiode and said charge-storage sections and
• controls transfer of electrons generated in said photodiode to said plurality of the charge-storage sections, wherein
• said gate structure is made up of three stages of gates,
• said three stages of gates have:
• a first-stage gate
• that is arranged adjacent to said photodiode and
• controls read-out of electrons generated in said photodiode;
• a second-stage gate
• that is adjacent to said first-stage gate on the rear stage of the gate at a predetermined gap,
• covers a channel region of the substrate comprising a P-type impurity concentration and P well regions having a higher P-type impurity doping concentration than remaining portions of the channel region, and
• controls moving of electrons read out by the readout control of said first-stage gate to said plurality of the charge-storage sections;
• and
• a third-stage gate constituted of a plurality of distribution gates
• that are adjacent to said second-stage gate on the rear stage of the gate at a predetermined gap,
• severally arranged corresponding to said plurality of the charge-storage sections, and
• perform control of distributing the electrons moved by the movement control of said second-stage gate severally to said plurality of the charge-storage sections,
• wherein
• the P wells resist an inversion while
• the remaining portions of the channel region invert
• when a gate voltage is applied to the second stage gate such that
• said second-stage gate
• allows electrons to intensively move to an area directly under the central portion of said second-stage gate and
• controls the movement of electrons to an area near the boundaries of said plurality of the third-stage gates,
• when a voltage is applied to said first-stage gate and said second-stage gate, and
• a region of a boundary between said each distribution gate in said third-stage gate is shorter than a gate dimension of said each distribution gate in planar view.