ChÃ cents teauneuf-les-Martigues is a commune of 11,900 people ( 2005 ) . It is found in the region Provence-Alpes-C Ã te d'Azur in the Bouches-du-Rh Ã ne department in the south of France . ChÃ cents teauneuf-les-Martigues is a commune in the Bouches-du-Rh Ã ne department in southern France .