The results of study of multilayer thin film structure using Rutherford Backscattering Spectroscopy (RBS) are presented. The structure 5(nm)Ta/30CuN/5Ta/3NiFe/16IrMn/2.0CoFe/0.9Ru/2.5CoFeB/2MgO/2.5CoFeB/10Ta/7Ru on SiO2 was used as a test sample. This kind of structure is using for MRAM fabrication. The RBS analysis of such samples might appear significant difficulties during measurement and interpretation of RBS spectra because of small layers thickness and overlay of peaks of elements with close masses. It was found that using different experimental conditions for RBS analysis one can obtain information about the density and thickness of each layer. The data about these parameters are presented.