Abstract. The composition, morphology, and electronic structure of SiO2 nanofilms of different thicknesses created by thermal oxidation on the Si(111) surface were studied in this work. It was shown that up to a thickness of 30-40 Å the film has an island character. At d ≥ 60 Å, a homogeneous continuous film of SiO2 is formed, the stoichiometric surface roughness does not exceed 1.5 – 2 nm. Regardless of the thickness of the SiO2 films, no noticeable interdiffusion of atoms is observed at the SiO2-Si boundary. The patterns of changes in the composition, the degree of surface coverage, and the energy of plasma oscillations were determined when the thickness of the SiO2/Si(111) films varied from 20 to 120 Å.