A single photon avalanche diode, SPAD, comprises an active area which is arranged to generate a photon triggered avalanche current. A cover is arranged on or above the active area. The cover shields the active area from incident photons. The cover comprises a stack of at least the first and a second metal layer. At least one of the metal layers, e.g. the first metal layer, comprises an aperture. The metal layers are arranged in the stack with respect to an optical axis such as to open an effective aperture along the optical axis. By way of the effective aperture a portion of the active area is exposed to incident photons being incident along the optical axis. The effective aperture is smaller than the aperture arranged in the first metal layer.