In one aspect, an image sensor is provided which includes an interlayer insulation film formed over a substrate including a light receiving device, a color filter formed over the interlayer insulation film, a protection film having a flat top face formed over the interlayer insulation film and the color filter, a buffer film having a convex top face formed over the protection film, and a microlens formed on the convex top face of the buffer film. The microlens has a refractive index which is greater than a refractive index of the buffer film and has a convex top face and a concave bottom face, where the concave bottom face of the microlens contacts the convex top face of the buffer film.