Planarization methods for maintaining planar surfaces in the fabrication of such devices as BAW devices and capacitors on a planar or planarized substrate are described. In accordance with the method, a metal layer is deposited and patterned, and an oxide layer is deposited using a high density plasma chemical vapor deposition (HDP CVD) process to a thickness equal to the thickness of the metal layer. The HDP CVD process provides an oxide layer on the patterned metal tapering upward from the edge of the patterned metal layer. Then, after masking and etching the oxide layer from the patterned metal layer, the patterned metal layer and surrounding oxide layer form a substantially planar layer, interrupted by small remaining oxide protrusions at the edges of the patterned layer. These small remaining oxide protrusions may be too small to significantly disturb the flatness of a further oxide or other layer or they may be further mitigated by the application of another HDP CVD oxide film.