Implementations disclosed herein generally relate to methods of forming silicon oxide films. The methods can include performing silylation on the surface of the substrate having terminal hydroxyl groups. The hydroxyl groups on the surface of the substrate are then regenerated using a plasma and H2O soak in order to perform an additional silylation. Further methods include catalyzing the exposed surfaces using a Lewis acid, directionally inactivating the exposed first and second surfaces and deposition of a silicon containing layer on the sidewall surfaces. Multiple plasma treatments may be performed to deposit a layer having a desired thickness.