A method for manufacturing a CMOS image sensor for near infrared detection. The method includes: a) providing a silicon wafer; b) performing a germanium implantation in a portion of a front side of the silicon wafer; c) performing an annealing so as to cause thermal diffusion of implanted germanium species, thereby forming silicon-germanium alloy lattice in a first silicon-germanium region exposed on the front side of the silicon wafer; d) carrying out the steps b) and c) one or more times; and e) forming first photodetector active areas in portions of the first silicon-germanium region downwards extending from the front side of the silicon wafer, wherein said first photodetector active areas are sensitive to both near infrared and visible radiations. The first photodetector active areas are formed also in portions of the silicon wafer extending below said portions of the first silicon-germanium region.