The present invention relates to a reactor and methods for performing single and in-situ multiple integrated circuit processing steps, including thermal CVD, plasma-enhanced chemical vapor deposition (PECVD), reactor self-cleaning, film etchback, and modification of profile or other film property by sputtering. The present invention also relates to a process for forming conformal, planar dielectric layers on integrated circuit wafers and to an in-situ multi-step process for forming conformal, planar dielectric layers that are suitable for use as interlevel dielectrics for multi-layer metallization interconnects.