a semiconductor substrate including a first principal surface and a second principal surface that oppose each other;

a plurality of avalanche photodiodes each including a light receiving region disposed at the first principal surface side of the semiconductor substrate, the avalanche photodiodes being distributed in a matrix at the semiconductor substrate, and arranged to operate in Geiger mode; and

a plurality of through-electrodes electrically connected to corresponding light receiving regions, and penetrating through the semiconductor substrate in a thickness direction,

wherein at the first principal surface of the semiconductor substrate, a groove is formed independently for each light receiving region to surround the light receiving region when viewed from a direction perpendicular to the first principal surface,

a distance between edges of the groove at the first principal surface is smaller than a width of the light receiving region,

a distance from the first principal surface to a bottom surface of the groove in the thickness direction is longer than a distance from the first principal surface to a PN junction included in the avalanche photodiode in the thickness direction,

the semiconductor substrate is formed with a through-hole in which the through-electrode is disposed, and

at the first principal surface, a distance from an edge of the through-hole to an edge, closer to the through-hole, of the edges of the groove is longer than the distance between the edges of the groove.