Densely packed monolayers of a charged virus are sandwiched in multilayer films of charged polyelectrolytes by successive adsorption of molecules of opposite charges. By small-angle X-ray scattering it is shown that films of well-defined thickness (+/-10 Angstrom) and with roughness of about 10 Angstrom can be prepared. It is demonstrated that the surface roughness created by particle deposition is smoothed by the following polymer adsorption steps. Very precise data on the lengths of sublayers are derived from suitable model fitting.