Focused ion beams are intensively used for device modification by local material removal and ion beam induced metal deposition. With shrinking dimensions on modern multilayer devices, the need for ion beam induced insulator deposition is increasing. In this article, tetramethoxysilane as a precursor for ion beam induced deposition has been investigated, The influence of beam parameters dwell time and loop time on the material deposition rate will be discussed and compared to model calculations. For optimized scanning conditions, a maximum deposition rate of 0.33 mu m(3)/nC was found. Insulating films were also deposited using an electron beam. The chemical composition and electrical properties of these films were compared with the films deposited by the ion beam, For electron beam deposition, the resistivity of the deposited films was 1 x 10(6) Psi cm which is two orders of magnitude higher than for ion beam deposited film.