Silicon layers were grown at 200 degreesC by reactive magnetron sputtering in a hydrogen-rich plasma (80% dilution). The samples were examined by Raman and infrared spectroscopies, as well as by transmission electron microscopy and optical transmission. In addition to the pronounced crystallization induced by the interactions with the H-based radicals, the incremental crystallization observed on the sample deposited in the region close to the cathode, where the radical density is high, appears due to the contribution of the incorporated Si nanopowders created in the surrounding plasma. The formation of these particles appeared, therefore, spatially limited because of its dependence on the radical density that is inhomogeneously distributed in the cathodesubstrate separating area. To some extent, this allows one to control their insertion, the growth rate and layer compactness, through variation of electrodes spacing, r.f. power and plasma pressure. The occurrence of both particle creation in the plasma and columnar growth in the bulk attests of the key role played by the highly sticking and reactive SiH2.