A photoelectric detection device detecting X or gamma radiation having a monolithic matrix detector made of a semiconductor material. One side of the detector includes a plurality of detecting electrodes, each electrode corresponding to one pixel. Each electrode is electrically connected to a reading circuit, and is separated from the adjacent electrodes by an insulating interpixel region. The detecting electrodes and the interpixel region are located at two different levels of the detector face. The detecting electrodes are positioned within deeply etched regions in the surface of the semiconductor material, which are surrounded by the interpixel regions.