Image sensor and method of fabricating the same

An image sensor comprising:

• a substrate having a first surface and a second surface opposite to the first surface;
• a pixel isolation pattern in the substrate, the pixel isolation pattern defining a plurality of unit pixels arranged two-dimensionally along a first direction and a second direction that intersects the first direction;
• photoelectric conversion regions within the respective unit pixels;
• element isolation patterns defining active regions within the respective unit pixels adjacent to the first surface;
• and
• a pad structure on the first surface,
• wherein
• the pixel isolation pattern comprises a first isolation portion extending in the second direction, a second isolation portion extending in the first direction, and a crossing portion where the first isolation portion and the second isolation portion intersect,
• the unit pixels comprise a first unit pixel, a second unit pixel separated from the first unit pixel by the first isolation portion, a third unit pixel separated from the first unit pixel by the second isolation portion, and a fourth unit pixel separated from the first unit pixel by the crossing portion, and
• the pad structure connects the active regions of the first to fourth unit pixels and does not overlap with the crossing portion.

An image sensor comprising:

• a substrate having a first surface and a second surface opposite the first surface;
• a pixel isolation pattern in the substrate, the pixel isolation pattern defining a first unit pixel, a second unit pixel adjacent to the first unit pixel in a first direction, a third unit pixel adjacent to the first unit pixel in a second direction intersecting the first direction, and a fourth unit pixel adjacent to the second unit pixel in the second direction and adjacent to the third unit pixel in the first direction;
• photoelectric conversion regions within the first to fourth unit pixels, respectively;
• element isolation patterns defining active regions within the first to fourth unit pixels adjacent to the first surface, respectively;
• first to fourth transfer gate structures disposed on the active regions of the first to fourth unit pixels, respectively;
• first to fourth floating diffusion regions within the active regions adjacent to the first to fourth transfer gate structures, respectively;
• and
• a first pad structure on the first surface, the first pad structure spaced apart from the first to fourth transfer gate structures and connecting the first to fourth floating diffusion regions,
• wherein the first pad structure comprises a first hole exposing the pixel isolation pattern disposed between the first unit pixel and the fourth unit pixel.