Image sensor and methods of driving and fabricating the same

1. An image sensor comprising:

a plurality of pixels, each of the plurality of pixels including:

a floating diffusion region;

a storage unit configured to (i) connect to the floating diffusion region and (ii) store photocharges therein; and

a selector including a switching element configured to receive first and second selection signals and selectively connect the storage unit to the floating diffusion region and disconnect the storage unit from the floating diffusion region in accordance with each of the first and second selection signals.

2. The image sensor of claim 1 , wherein the storage unit includes a capacitive element electrically connected to the floating diffusion region.

3. The image sensor of claim 1 , wherein each of the capacitive element and the switching element comprises a transistor.

4. The image sensor of claim 3 , wherein the switching element includes a first MOS transistor;

the capacitive element includes a second MOS transistor having a gate electrically connected to a drain of the first MOS transistor;

the first selection signal is applied to a gate or a source of the first MOS transistor;

the second selection signal is applied to the other of the gate or source of the first MOS transistor; and

the floating diffusion region is connected to a source or drain of the second MOS transistor.

5. The image sensor of claim 1 , further comprising:

a photoelectric converter configured to receive light and generate the photocharges;

a transfer unit configured to transfer the photocharges generated by the photoelectric converter to the floating diffusion region; and

an output unit configured to amplify and output a signal corresponding to the photocharges in the floating diffusion region and (when activated) the storage unit.

6. The image sensor of claim 5 , comprising a plurality of light sensing units commonly connected to the floating diffusion region, wherein each light sensing unit includes the photoelectric converter and the transfer unit.

7. The image sensor of claim 1 , wherein the first and second selection signals are configured to select a row and a column of the pixel.

8. The image sensor of claim 7 , wherein the storage unit further comprises a capacitor.

9. The image sensor of claim 1 , wherein each of the plurality of pixels further includes a select transistor configured to select the pixel in response to a predetermined address.

10. A method for driving an image sensor having a plurality of pixels, each pixel having a floating diffusion region with an adjustable capacitance, the method comprising:

increasing a capacitance of the floating diffusion region for a selected pixel of the plurality of pixels by selectively driving a switching element with first and second selection signals configured to (i) select a row and a column of the pixel and (ii) couple a capacitive element to the floating diffusion region;

outputting a voltage on the floating diffusion region of the selected pixel as a reference voltage;

transferring photocharges generated by a photoelectric converter to the floating diffusion region of the selected pixel having the increased capacitance; and

outputting a voltage of the floating diffusion region of the selected pixel having the increased capacitance as a sensing voltage.

11. The method of claim 10 , further comprising resetting an electrical potential of the floating diffusion region to a given voltage before outputting the voltage on the floating diffusion region as a reference voltage.

12. An image sensor comprising:

a plurality of pixels, each of the plurality of pixels including:

a capacitive element selectively and electrically connectable to a floating diffusion region in the pixel; and

a switching element configured to (i) be selectively driven by first and second selection signals, and (ii) couple the capacitive element to the floating diffusion region, wherein the first and second selection signals are configured to select a row and a column of the pixel.

13. The image sensor of claim 12 , wherein the capacitive element comprises a first transistor.

14. The image sensor of claim 13 , wherein the first transistor is a first MOSFET transistor.

15. The image sensor of claim 14 , wherein the capacitive element further comprises a capacitor.

16. The image sensor of claim 15 , wherein:

the first MOSFET transistor has a gate electrically connected to a drain of the second MOSFET transistor;

the first selection signal is applied to a gate or a source of the second MOSFET transistor;

the second selection signal is applied to the other of the gate or source of the second MOSFET transistor; and

the floating diffusion region is connected to a source or drain of the first MOSFET transistor.

17. The image sensor of claim 14 , further comprising:

a photoelectric converter configured to receive light and generate the photocharges;

a transfer unit configured to transfer the photocharges generated by the photoelectric converter to the floating diffusion region; and

an output unit configured to amplify and output a signal corresponding to the photocharges in the floating diffusion region and (when activated) the storage unit.

18. The image sensor of claim 17 , comprising a plurality of light sensing units commonly connected to the floating diffusion region, wherein each light sensing unit includes the photoelectric converter and the transfer unit.

19. The image sensor of claim 12 , wherein the switching element comprises a second transistor.

20. The image sensor of claim 19 , wherein the second transistor is a second MOSFET transistor.