A method is provided for forming a stable thin film on a substrate. The method includes depositing a co-polymer composition having a first component and a second component onto a substrate to form a stable film having a first thickness. The first component has first dielectric properties not enabling the first component by itself to produce the stable film having the first thickness. However, the second component has second dielectric properties which impart stability to the film at the first thickness. In a preferred embodiment, the second component includes a leaving group, and the method further includes first thermal processing the film to cause a solvent but not the leaving group to be removed from the film, after which second thermal processing is performed to at least substantially remove the leaving group from the film. As a result, the film is reduced to a second thickness smaller than the first thickness, and the film remains stable during both the first and the second thermal processing.