The formation of crystalline silicon nanoparticles was investigated by means of Raman spectroscopy. SiO(x) ( x = 1 and x = 1.5). films deposited by electron-gun evaporation onto silica substrates were submitted to post-deposition thermal treatments at 1000 and 1100 degrees C for various times. From line-shape analysis of the Raman band, it appeared that the crystalline volume fraction never excessed 30% for annealing at 1000 degrees C, while the mean diameter remained almost constant. Complete crystallisation was achieved after annealing at 1100 degrees C, accompanied by an increase of the nanoparticle size. Mean diameters of the nanoparticles obtained from Raman spectra analysis along the two main confinement models, Richter et al., Campbell, Fauchet model and bond-polarizability model, were discussed and compared to values deduced from transmission electron microscopy measurements.