Photoelectric conversion apparatus and image pickup system

A photoelectric conversion apparatus comprises a plurality of units each including first (charge generation region 102), second (charge storage region 105) and third (charge detection region 103) n type impurity regions in a semiconductor layer; a dielectric region 130 surrounded by an insulator 2141-2144, the dielectric being formed of a different material to the insulator; and a first light-shielding layer 109 covering the charge storage region and having a first type opening 190 located above the charge generation region. The first light-shielding layer has second type openings (191, 192, Figure 2B) of a different shape to the first opening, in which contact plugs are disposed. In a first unit PXL, the charge generation region is able to receive light through the first type opening of the first light-shielding layer. In second units OBA and OBB, the charge generation region is covered with a second light-shielding layer 231 to provide an optical black reference signal for black-level correction.