AVALANCHE PHOTODIODE SENSOR, AND ELECTRONIC DEVICE

An avalanche photodiode (APD) sensor includes a photoelectric conversion region disposed in a substrate and that converts light incident to a first side of the substrate into electric charge, and a cathode region disposed at a second side of the substrate. The second side is opposite the first side. The APD sensor includes an anode region disposed at the second side of the substrate, a first region of a first conductivity type disposed in the substrate, and a second region of a second conductivity type disposed in the substrate. The second conductivity type is different than the first conductivity type. In a cross-sectional view, the first region and the second region are between the photoelectric conversion region and the second side of the substrate. In the cross-sectional view, an interface between the first region and the second region has an uneven pattern.