A semiconductor device includes: a photosensitive section essentially composed of a PN junction between a semiconductor multilayer structure of the first conductivity type and a first semiconductor layer of the second conductivity type; and a partitioning portion for splitting the photosensitive section into a plurality of regions. The semiconductor multilayer structure of the first conductivity type includes: a semiconductor substrate of the first conductivity type; a first semiconductor layer of the first conductivity type; and a second semiconductor layer of the first conductivity type. The partitioning portion includes a third semiconductor layer of the first conductivity type extending from the first semiconductor layer of the second conductivity type so as to reach the second semiconductor layer of the first conductivity type.