Image sensing device

1. An image sensing device comprising:

a pixel array including a plurality of unit pixel blocks each including a plurality of unit image sensing pixels arranged in the pixel array and structured to convert light into photocharges,

wherein each of the unit pixel blocks includes:

a first sub-pixel block including a first floating diffusion region structured to hold the photocharges and a plurality of unit image sensing pixels sharing the first floating diffusion region; and

a conversion gain capacitor arranged adjacent to one side of the first sub-pixel block, and structured to include an impurity region disposed in a substrate and coupled to an input node that receives a conversion gain signal, and a gate structured to surround at least a portion of a top surface of the impurity region over the substrate and coupled to the first floating diffusion region to change a gain of the first floating diffusion region in response to a change in the conversion gain signal.

2. The image sensing device according to claim 1 , wherein:

the gate has a rectangular ring shape structured to surround the impurity region.

3. The image sensing device according to claim 1 , wherein each of the unit pixel blocks further includes:

a second sub-pixel block configured to include a second floating diffusion region structured to hold the photocharges and coupled to the first floating diffusion region, and a plurality of unit image sensing pixels sharing the second floating diffusion region.

4. The image sensing device according to claim 3 , wherein:

the conversion gain capacitor is disposed between the first sub-pixel block and the second sub-pixel block.

5. The image sensing device according to claim 3 , wherein each of the unit pixel blocks further includes:

a reset transistor configured to initialize the first and second floating diffusion regions based on a reset signal.

6. The image sensing device according to claim 5 , wherein:

the reset transistor is disposed adjacent to the conversion gain capacitor and between the first sub-pixel block and the second sub-pixel block.

7. The image sensing device according to claim 5 , wherein each of the unit pixel blocks further includes:

a device isolation region structured to electrically isolate the conversion gain capacitor, the reset transistor, and the first floating diffusion region from each other.

8. The image sensing device according to claim 7 , wherein:

the device isolation region includes an impurity region.

9. The image sensing device according to claim 1 , wherein each of the unit image sensing pixels includes:

a photoelectric conversion element configured to generate photocharges by converting incident light; and

a transfer transistor configured to transmit the photocharges generated by the photoelectric conversion element to the first floating diffusion region based on a transmission signal.

10. The image sensing device according to claim 1 , wherein each of the plurality of unit pixel blocks includes:

a plurality of unit image sensing pixels arranged to surround the first floating diffusion region while being spaced apart from each other by a predetermined distance.

11. An image sensing device comprising:

at least one photoelectric conversion element configured to generate photocharges by converting incident light;

a floating diffusion region configured to store the photocharges generated by the at least one photoelectric conversion element;

at least one transfer transistor configured to transfer the photocharges to the floating diffusion region based on a transmission signal; and

a conversion gain capacitor coupled to the floating diffusion region to adjust capacitance associated with the floating diffusion region based on a conversion gain signal to switch between different conversion gain values,

wherein the conversion gain capacitor includes:

an impurity region disposed in a substrate and configured to receive the conversion gain signal; and

a gate structured to surround at least a portion of a top surface of the impurity region over the substrate and coupled to the floating diffusion region.

12. The image sensing device according to claim 11 , wherein:

the gate has a rectangular ring shape structured to surround the impurity region.

13. The image sensing device according to claim 11 , wherein the at least one transfer transistor includes:

a plurality of transfer transistors arranged to be mapped to at least one photoelectric conversion element to transfer photocharges generated by a corresponding photoelectric conversion element to the floating diffusion region.

14. The image sensing device according to claim 11 , wherein the at least one transfer transistor includes:

a plurality of transfer transistors spaced apart from each other by a predetermined distance and arranged to surround the floating diffusion region.

15. The image sensing device according to claim 11 , further comprising:

a reset transistor configured to initialize the floating diffusion region based on a reset signal.

16. The image sensing device according to claim 15 , wherein:

the reset transistor is disposed adjacent to the conversion gain capacitor and is coupled to the gate through a conductive line.

17. The image sensing device according to claim 15 , further comprising:

a device isolation region structured to electrically isolate the conversion gain capacitor, the reset transistor, and the floating diffusion region from each other.

18. The image sensing device according to claim 17 , wherein:

the device isolation region includes an impurity region.