A method of etching exposed silicon oxide on patterned heterogeneous structures is described and includes a gas phase etch using plasma effluents formed in a remote plasma. The remote plasma excites a fluorine-containing precursor in combination with an oxygen-containing precursor. Plasma effluents within the remote plasma are flowed into a substrate processing region where the plasma effluents combine with water vapor or an alcohol. The combination react with the patterned heterogeneous structures to remove an exposed silicon oxide portion faster than an exposed silicon nitride portion. The inclusion of the oxygen-containing precursor may suppress the silicon nitride etch rate and result in unprecedented silicon oxide etch selectivity.