A method for fabricating gate electrodes and gate interconnects with a protective silicon oxide or silicon nitride cap and spacer formed by high density plasma chemical vapor deposition (HDPCVD). Silicon oxide or silicon nitride is deposited in a reaction zone of a HDPCVD reactor while providing two or more selected substrate bias powers, source powers and/or selected gas mixtures to tailor the shape and thickness of the film for desired applications. In one embodiment, a low bias power of below 500 Watts is provided in a first stage HDPCVD and the bias power is then increased to between 500 and 3000 Watts for a second stage to produce a protective film having thin sidewall spacers for enhanced semiconductor device density and a relatively thick cap.