SiH4 and H2O2 have been successfully used for the deposition of silicon dioxide for shallow trench isolation. With this chemistry, it is possible to fill up trenches without voids up to an aspect ratio 2.3:1. The very good gap filling is due to the presence of SIGH groups in the oxide film. To obtain a density close to that of thermal oxide, the film must be annealed at high temperature. The electrical characteristics are equivalent to those obtained using thermal silicon dioxide.