Image sensing device

1. An image sensing device comprising:

a pixel array including a plurality of unit pixels consecutively arranged and structured to generate an electrical signal in response to incident light by performing photoelectric conversion of the incident light,

wherein the unit pixels are isolated from each other by first device isolation structures, and each of the unit pixels includes:

a photoelectric conversion element structured to generate photocharges by performing photoelectric conversion of the incident light;

a floating diffusion region structured to receive the photocharges;

a transfer transistor structured to transfer the photocharges generated by the photoelectric conversion element to the floating diffusion region; and

a well tap region structured to apply a bias voltage to a well region,

wherein the well tap region is disposed at a center portion of a corresponding unit pixel.

2. The image sensing device according to claim 1 , wherein the plurality of unit pixels are arranged to be grouped into a plurality of unit pixel groups that are consecutively arranged, and wherein the floating diffusion regions of the unit pixels in each of the unit pixel groups are coupled to a common floating diffusion node through a conductive line.

3. The image sensing device according to claim 2 , wherein the unit pixels in each of the unit pixel groups are arranged in a 2×2 matrix array.

4. The image sensing device according to claim 2 , wherein the unit pixels in each of the unit pixel groups include a plurality of first unit pixels and a second unit pixel, and wherein:

each of the first unit pixels includes a source follower transistor configured to generate an amplification signal corresponding to a voltage at the common floating diffusion node, and a selection transistor configured to output the amplification signal to an output node in response to a selection signal; and

the second unit pixel includes a reset transistor configured to reset the common floating diffusion node in response to a reset signal.

5. The image sensing device according to claim 4 , wherein each of the first unit pixels includes first to third active regions divided by a second device isolation structure, and wherein:

the first active region is disposed at a center portion of the first unit pixels, and

the second and third active regions are disposed in an edge region of the first unit pixels and surround the first active region.

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

the well tap region is formed in the first active region;

the source follower transistor and the selection transistor are formed in the second active region; and

the transfer transistor and the floating diffusion region are formed in the third active region.

7. The image sensing device according to claim 4 , wherein the second unit pixel includes fourth and fifth active regions divided by a third device isolation structure, and wherein:

the fourth active region is disposed at a center portion of the second unit pixel; and

the fifth active region is disposed in an edge region of the second unit pixel and surround the fourth active region.

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

the fourth active region includes the well tap region; and

the fifth active region includes the reset transistor, the transfer transistor and the floating diffusion region.

9. The image sensing device according to claim 4 , wherein the second unit pixel includes sixth to eighth active regions divided by a fourth device isolation structure, and wherein:

the sixth active region is disposed at a center portion of the second unit pixel, and

the seventh and eighth active regions are disposed in an edge region of the second unit pixel and surround the sixth active region.

10. The image sensing device according to claim 9 , wherein:

the sixth active region includes the well tap region;

the seventh active region includes the reset transistor; and

the eighth active region includes the transfer transistor and the floating diffusion region.

11. The image sensing device according to claim 1 , wherein the plurality of unit pixels includes first to sixth unit pixels and wherein:

the first unit pixel includes a first source follower transistor and a first selection transistor;

the second unit pixel includes a second source follower transistor and a second selection transistor;

the third unit pixel further includes a third source follower transistor and a third selection transistor;

the fourth unit pixel further includes a reset transistor;

the fifth unit pixel further includes a fourth source follower transistor and a fourth selection transistor; and

the sixth unit pixel further includes a fifth source follower transistor and a fifth selection transistor,

wherein the floating diffusion regions of the first to fourth unit pixels are coupled to a common floating diffusion node through a conductive line, and the common floating diffusion node is coupled to gates of the third, fifth, and sixth source follower transistors through a conductive line.

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

the first to fourth unit pixels are arranged in a 2×2 matrix array while being arranged adjacent to each other;

the fifth unit pixel is located adjacent to the third unit pixel in a first direction; and

the sixth unit pixel is located adjacent to the fifth unit pixel in a second direction perpendicular to the first direction.