Buried hexagonal YSi2 layers were formed using 100 keV yttrium ions to a dose of 1×1018 Y+cm-2 implanted into (111) oriented silicon wafers by a metal vapor vacuum arc ion source. The structure and infrared absorption spectra of the compound layers have been investigated by x-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS) and Fourier transform infrared (FT-IR) transmittance spectrometry. It was shown that YSi2 has been directly formed during the implantation. A tendency of preferred growth was found in the following process of infrared irradiation. RBS measurements revealed that, after infrared irradiation, the average atomic density ratio of Si to Y in the buried layers decreases from 24 down to around 20, which is close to the stoichiometry of hexagonal YSi2. The characteristic vibration absorption spectra of the silicides have been obtained by FT-IR transmittance measurements.