A solid-state image sensor including a semiconductor substrate containing a plurality of photoelectric conversion elements, the sensor comprising: a first insulating film which is arranged on the semiconductor substrate and has a plurality of openings, each of the plurality of openings being arranged on one of the plurality of photoelectric conversion elements; and a plurality of insulator portions (9a, 9b) which have a refractive index higher than a refractive index of the first insulating film, each of the plurality of insulator (9a, 9b) portions being arranged in one of the plurality of openings such that the openings are completely filled with the insulator portions; and a second insulating film which has a refractive index higher than the refractive index of the first insulating film, wherein the second insulating film is arranged directly on upper surfaces of the plurality of insulator portions (9a, 9b) and an upper surface of the first insulating film; and a third insulating film which has a refractive index lower than a refractive index of the second insulating film and is arranged in contact with an upper surface of the second insulating film 10b), a plurality of color filters (12R, 12G, 12B) comprising a red color filter, a green color filter and a blue color filter on the third insulating film, wherein each of the photoelectric conversion elements corresponds to one of the plurality of color filters such that light passing through one of the color filters enters the corresponding insulator portion, and the plurality of color filters pass the light of corresponding wavelength bands; characterized in that letting n be the refractive index of the second insulating film, and t be a thickness of the second insulating film on at least the upper surface of the first insulating film, a relation t < λ/n is satisfied for one of the wavelengths λ of the wavelength bands, and the upper surface of the second insulating film is a smooth continuous surface. a first insulating film which is arranged on the semiconductor substrate and has a plurality of openings, each of the plurality of openings being arranged on one of the plurality of photoelectric conversion elements; and a plurality of insulator portions (9a, 9b) which have a refractive index higher than a refractive index of the first insulating film, each of the plurality of insulator (9a, 9b) portions being arranged in one of the plurality of openings such that the openings are completely filled with the insulator portions; and a second insulating film which has a refractive index higher than the refractive index of the first insulating film, wherein the second insulating film is arranged directly on upper surfaces of the plurality of insulator portions (9a, 9b) and an upper surface of the first insulating film; and a third insulating film which has a refractive index lower than a refractive index of the second insulating film and is arranged in contact with an upper surface of the second insulating film 10b), a plurality of color filters (12R, 12G, 12B) comprising a red color filter, a green color filter and a blue color filter on the third insulating film, wherein each of the photoelectric conversion elements corresponds to one of the plurality of color filters such that light passing through one of the color filters enters the corresponding insulator portion, and the plurality of color filters pass the light of corresponding wavelength bands; characterized in that letting n be the refractive index of the second insulating film, and t be a thickness of the second insulating film on at least the upper surface of the first insulating film, a relation t < λ/n is satisfied for one of the wavelengths λ of the wavelength bands, and the upper surface of the second insulating film is a smooth continuous surface.