A sensor includes a substrate provided with a circuit element forming region and a photodiode forming region, the substrate having a silicon substrate, an insulating layer on the silicon substrate, and a silicon layer on the insulating layer; a photodiode in the silicon layer; a circuit element in the silicon layer; a first interlayer insulating film formed over the silicon layer; a first light-shielding film on the first interlayer film and having an opening in the photodiode forming region; and a first inter-region light-shielding plug arranged between the two regions, for connecting the silicon substrate and the first light-shielding film.