Provided herein are methods and apparatus for improved flowable dielectric deposition on substrate surfaces. The methods involve improving nucleation and wetting on the substrate surface without forming a thick high wet etch rate interface layer. According to various embodiments, the methods may include single or multi-stage remote plasma treatments of a deposition surface. In some embodiments, a treatment may include exposure to both a reducing chemistry and a hydrogen-containing oxidizing chemistry. Apparatus for performing the methods are also provided.