A solid-state image sensor including photoelectric conversion elements, comprises a first insulating film arranged on a substrate and having openings arranged on the respective elements, insulator portions having a refractive index higher than that of the first insulating film and arranged in the respective openings, a second insulating film arranged on upper surfaces of the insulator portions and an upper surface of the first insulating film, and a third insulating film having a refractive index lower than that of the second insulating film and arranged in contact with an upper surface of the second insulating film, wherein letting λ be a wavelength of entering light, n be the refractive index of the second insulating film, and t be a thickness of the second insulating film in at least part of a region on the upper surface of the first insulating film, a relation t