Image sensor

An image sensor, comprising:

• a substrate including a first surface and a second surface, wherein the first surface and the second surface are opposite to each other in a first direction;
• a plurality of pixels, each pixel of the plurality of pixels including a photoelectric conversion area in the substrate;
• and
• a transfer gate electrode on one pixel of the plurality of pixels, wherein the transfer gate electrode includes a first extension, a second extension, and a third extension, wherein the first extension, the second extension, and the third extension are above the photoelectric conversion area of the one pixel and extending into the substrate,
• wherein the substrate contains impurities of a first conductivity type,
• wherein the photoelectric conversion area contains impurities of a second conductivity type different from the first conductivity type,
• wherein a first depth of the first extension in the substrate is larger than each of a second depth of the second extension in the substrate and a third depth of the third extension in the substrate, and
• wherein a spacing between the first extension and a center of the photoelectric conversion area on the first surface of the substrate is smaller than each of a spacing between the second extension and the center of the photoelectric conversion area on the first surface of the substrate and a spacing between the third extension and the center of the photoelectric conversion area on the first surface of the substrate.

An image sensor, comprising:

• a substrate including a first surface and a second surface, wherein the first surface and the second surface are opposite to each other in a first direction;
• a plurality of pixels, each pixel of the plurality of pixels including a photoelectric conversion area in the substrate;
• a pixel isolation pattern in the substrate so as to define the plurality of pixels;
• a color filter on the second surface of the substrate;
• a micro lens on the color filter;
• a transfer gate electrode on one pixel of the plurality of pixels, wherein the transfer gate electrode overlaps the photoelectric conversion area of the one pixel in the first direction, and the transfer gate electrode includes a first extension, a second extension, and a third extension, wherein the first extension, the second extension, and the third extension are extending from the first surface of the substrate into the substrate;
• and
• a floating diffusion area in the substrate, wherein the floating diffusion area is in a corner of each of the plurality of pixels,
• wherein the substrate contains impurities of a first conductivity type,
• wherein the photoelectric conversion area contains impurities of a second conductivity type different from the first conductivity type,
• wherein the first extension is adjacent to a center of the photoelectric conversion area on the first surface of the substrate,
• wherein each of the second extension and the third extension is adjacent to the floating diffusion area,
• wherein a bottom surface of the first extension is at a vertical center of the photoelectric conversion area in the first direction, and
• wherein each of a bottom surface of the second extension and a bottom surface of the third extension are spaced apart from the photoelectric conversion area in the first direction.