The elastic properties of new materials used as low-k dielectrics (SiOC:H) and barrier layers (SiCN:H and SiC:H) in the construction of very large scale integrated electronic circuits have been investigated by Brillouin light scattering. For comparison, also silicon dioxide and silicon nitride films have been analysed. Both surface and bulk acoustic waves have been revealed and their phase velocity measured, achieving a complete elastic characterization of the film materials. SiOC:H is by far the softer material, because of the presence of many organic groups. SiCN:H is very similar to silicon dioxide and other conventional silicate glasses, while SiC:H is intermediate between the former two. All these materials are, however, much softer than silicon nitride. The found values of the elastic moduli are appreciably lower than previous data obtained by nano-indentation technique on similar films. (c) 2005 Elsevier B.V. All rights reserved.