be identical according to an embodiment thin layer 41 is a single crystal silicon layer having a thickness from 3 to 5 u03bcm and the insulating layer filling the interval between pads is a silicon oxide layer it should be noted that the optical indexes of silicon and of silicon oxide are clearly differentiated as they are respectively close to 4 and to 1 45 which is favorable to the obtaining of an efficient optic network for a photodiode associated with a red filter unevennesses 41 will for example have the following characteristics period u03bb on the order of from 350 to 400 nm height d of the pads on the order of from 50 to 300 nm ratio between the pad width and the distance between pads close to 1 specific embodiments of the present invention have been described various alterations and modifications will occur to those skilled in the art in particular the present invention has been described as applied to a specific type of back side sensor based on photodiodes this sensor is likely to have various alterations further all back side sensors are confronted to the same problem and the solution provided herein also applies to other back side sensors for example the present invention also applies to sensors based on phototransistors or on photogates further.