[en] In this work Si samples implanted with nitrogen (N⁺ or N₂⁺) at a dose of 10¹⁷ cm^-2 are characterized by Raman spectroscopy and cross section transmission electron microscopy (XTEM). The correlation between the Raman spectra obtained with different excitation wavelengths and XTEM observations allows to determine the structural features related to the layers contributing to the total spectra. The evolution of these features with the annealing treatments (up to 1,150 C) is studied. The results obtained show, after the annealing treatment at the highest temperature, the presence of silicon nitride precipitates in the silicon subsurface region, and the formation of a nitrogen rich polycrystalline Si layer with Si₃N, grains. The Raman spectra from the subsurface region show a remaining shift of -0.15 cm^-1 when compared to the spectra from unimplanted Si. This shift, together with the similar shape of both Raman lines, suggests the presence in this region of an average tensile stress of 37.5 MPa