Image sensing device

An image sensing device comprising:

• a first unit pixel including a first photoelectric conversion element configured to generate photocharges in response to incident light, and a first floating diffusion region configured to receive photocharges generated by the first photoelectric conversion element;
• a second unit pixel including a second photoelectric conversion element configured to generate photocharges in response to incident light, and a second floating diffusion region configured to receive photocharges generated by the second photoelectric conversion element;
• a third unit pixel including a third photoelectric conversion element configured to generate photocharges in response to incident light, and a third floating diffusion region configured to receive photocharges generated by the third photoelectric conversion element;
• and
• a fourth unit pixel including a fourth photoelectric conversion element configured to generate photocharges in response to incident light, and a fourth floating diffusion region configured to receive photocharges generated by the fourth photoelectric conversion element,
• wherein
• the first to fourth unit pixels are isolated from each other by a first device isolation structure,
• the first to fourth floating diffusion regions are coupled to a common floating diffusion node through conductive lines, and
• at least one unit pixel among the first to fourth unit pixels includes a conversion gain transistor coupled to the common floating diffusion node and configured to adjust capacitance of the common floating diffusion node in response to a gain control signal provided to the conversion gain transistor.