Abstract: Image sensors and fabrication methods thereof. For example, the image sensor may include a first substrate having a first surface and a second surface that are opposite to each other, a plurality of pixels provided in the first substrate and arranged in pixel groups, each pixel group including four pixels arranged in two columns and two rows, a pixel separation structure in the first substrate and including a pixel group separation part that separates each pixel group from adjacent pixel groups and a pixel separation part that separates the pixels in each pixel group from each other, and a plurality of microlenses on the first surface and respectively overlapping the plurality of pixel groups. Each of the microlenses includes a central part that has a first curvature and an edge part that has a second curvature. The first curvature is less than the second curvature.

Abstract: An image sensor includes a substrate having first and second surfaces opposing each other; photodiodes in the substrate; circuit and wiring structures below the first surface of the substrate; an insulating structure on the second surface of the substrate; a plurality of color filters on the insulating structure; and a grid structure on the insulating structure, wherein at least a portion of the grid structure is between adjacent color filters of, wherein the plurality of color filters include first and second color filters configured to selectively transmit light of different wavelength spectra associated with different colors, wherein the insulating structure includes a first and second regions having respective, different first and second thicknesses, and a boundary region between the first region and the second region that vertically overlaps the first color filter and is horizontally offset from a vertical central axis of the grid structure.

Abstract: An image sensor includes a substrate, a pixel isolation pattern in the substrate and defining unit pixel regions in the substrate, color filters on the substrate and corresponding to the unit pixel regions, respectively, a low-refractive index pattern between adjacent color filters of the color filters to at least partially isolate the adjacent color filters from direct contact with each other, an insulating structure between the substrate and the color filters, and a light blocking pattern vertically overlapping with the pixel isolation pattern. The light blocking pattern is within the insulating structure and is isolated from direct contact with the low-refractive index pattern.