A process is managed by creating a future revision of a base. This implantable medical device to be implanted at an implantation site comprises a proximal end, a central portion and a distal end, characterized in that it comprises, at its proximal end, at least one means for positioning the implantable device at a precise point of a branching of a blood vessel, such as a coronary artery. A concentration of impurities in the upper silicon layer is higher than that of the lower silicon layer.