Aspects of the disclosure pertain to methods of depositing silicon oxide layers on substrates. In embodiments, silicon oxide layers are deposited by flowing a silicon-containing precursor having a Si—O bond, an oxygen-containing precursor and a second silicon-containing precursor, having both a Si—C bond and a Si—N bond, into a semiconductor processing chamber to form a conformal liner layer. Upon completion of the liner layer, a gap fill layer is formed by flowing a silicon-containing precursor having a Si—O bond, an oxygen-containing precursor into the semiconductor processing chamber. The presence of the conformal liner layer improves the ability of the gap fill layer to grow more smoothly, fill trenches and produce a reduced quantity and/or size of voids within the silicon oxide filler material.