An optical sensor arrangement, in particular an optical proximity sensor arrangement comprises a three-dimensional integrated circuit further comprising a first layer comprising a light-emitting device, a second layer comprising a light-detector and a driver circuit. The driver circuit is electrically connected to the light-emitting device and to the light-detector to control the operation of the light-emitting device and the light-detector. A mold layer comprising a first light-barrier between the light-emitting device and the light-detector configured to block light from being transmitted directly from the light-emitting device to the light-detector.