Surface related phenomena of O3-TEOS subatmospheric chemical vapor deposition (SACVD) films were systematically studied on different types of plasma enhanced CVD (PECVD) oxides. The PECVD oxides are part of a new and in situ 2 step gap fill process consisting of a thin PECVD underlayer and a thick O3-TEOS SACVD oxide being proposed for advanced ULSI devices. Differences in deposition rates, wet etch rate, surface morphology, and stress-temperature behavior of O3-TEOS SACVD films deposited on PECVD oxide underlayers and bare silicon substrates were evaluated. For the PECVD underlayers which render surface dependence for the O3-TEOS SACVD film, various plasma treatments of the underlayer was used to eliminate the effect. An extensive analysis of the surface and bulk properties of these PECVD oxide underlayers suggests that the occurrence of the surface dependence effects can be attributed to the presence of electronegative species such as fluorine on the surface of the PECVD oxide underlayer.