Charge transferring device and charge transferring method which can reduce floating diffusion capacitance

A charge transferring device comprising:

• a detection MOSFET for detecting a signal charge;
• and
• a reset MOSFET for removing said signal charge after said signal charge is detected, wherein said reset MOSFET comprises:
• a floating diffusion layer to which said signal charge is transferred;
• an impurity layer to which a reset voltage is applied;
• and
• a reset gate electrode to which a reset signal is supplied, and
• wherein said detection MOSFET includes a detection gate electrode connected with said floating diffusion layer, and
• wherein said floating diffusion layer comprises:
• a first semiconductor region;
• and
• a second semiconductor region whose impurity concentration is lower that that of said first semiconductor region, and
• wherein said impurity concentration of said first semiconductor region is set to a concentration such that said first semiconductor region is not depleted at a voltage lower than said reset voltage when said reset signal is supplied to said reset gate electrode,
• wherein said impurity concentration of said second semiconductor region is set to a concentration such that said second semiconductor region is depleted when said reset signal is supplied to said reset gate electrode, and
• wherein said first semiconductor region is provided to extend in a transfer direction of said signal charge, in said floating diffusion layer,
• wherein said first semiconductor region and said second semiconductor region are materials having a same type of majority carrier.

A charge transferring device comprising:

• a detection MOSFET for detecting a signal charge;
• and
• a reset MOSFET for removing said signal charge after said signal charge is detected, wherein said resect MOSFET comprises:
• a floating diffusion layer to which said signal charge is transferred;
• an impurity layer to which a reset voltage is applied;
• and
• a reset gate electrode to which a reset signal is supplied, and
• wherein said detection MOSFET includes a detection gate electrode connected with said floating diffusion layer, and
• wherein said floating diffusion layer comprises:
• a first semiconductor region;
• a second semiconductor region whose impurity concentration is lower than that of said first semiconductor region;
• and
• a third semiconductor region whose impurity concentration is higher than that of said first semiconductor region, and
• wherein said first semiconductor region is provided without being in contact with an element separating region, and is provided to extend in a transfer direction of said signal charge, in said floating diffusion layer, and an impurity concentration of said first semiconductor region is set to a concentration such that said first semiconductor region is not depleted at a voltage lower than said reset voltage when said reset signal is supplied to said reset gate electrode,
• wherein said second semiconductor region is provided to be in contact with said element separating region, an impurity concentration of said second semiconductor region being set to a concentration such that said second semiconductor region is depleted when said reset signal is supplied to said reset gate electrode, and
• wherein said third semiconductor region is provided near the center of said floating diffusion layer such that at least a part of said third semiconductor region overlaps with said first semiconductor region, and is connected to said detection gate electrode.

A charge transferring device comprising:

• means for setting a floating diffusion layer to a reset potential in response to a reset signal;
• means for forming a well corresponding to said reset potential in said floating diffusion layer;
• means for transferring a signal charge to said well;
• means for detecting said signal charge transferred to said well;
• means for reducing a floating diffusion layer capacitance in said floating diffusion layer;
• and
• means for preventing said floating diffusion layer from being depleted in a potential lower than said reset potential,
• wherein said means for reducing said floating diffusion capacitance includes a first semiconductor region provided without being in contact with an element separating region, and a second semiconductor region which is provided to be in contact with said element separating region and whose impurity concentration is set to be lower than that of said first semiconductor region,
• wherein said first and second semiconductor regions are included in said floating diffusion layer,
• wherein said impurity concentration of said second semiconductor is set to a concentration such that said second semiconductor region is depleted, when said floating diffusion layer is set to said reset potential, and
• wherein said first semiconductor region is provided to extend in a transfer direction of said signal charge, in said floating diffusion layer, and
• wherein said floating diffusion layer further comprises a third semiconductor region whose impurity concentration is higher than that of said first semiconductor region.