A rapid vapor deposition (RVD) method conformally deposits a dielectric material on small features of a substrate surface. The resulting dielectric film has a low dielectric constant, low wet etch rate, low film shrinkage and low stress hysteresis, appropriate for various integrated circuit dielectric gap fill applications such as shallow trench isolation. The method includes the following two principal operations: depositing a thin conformal and saturated layer of aluminum-containing precursor over some or all of the substrate surface; and exposing the saturated layer of aluminum-containing precursor to a silicon-containing precursor gas to form a dielectric layer. In some cases, the substrate temperatures during contact with silicon-containing precursor are greater than about 250 degree Celsius to produce an improved film. In other cases, post-deposition anneal process may be used to improve properties of the film. Generally an inert gas purge is employed between the introduction of reactant gases to remove byproducts and unused reactants. These operations can be repeated to deposit multiple layers of dielectric material until a desired dielectric thickness is achieved.