Exemplary methods of etching a silicon-containing material may include flowing a first fluorine-containing precursor into a remote plasma region of a semiconductor processing chamber. The methods may include flowing a sulfur-containing precursor into the remote plasma region of the semiconductor processing chamber. The methods may include forming a plasma within the remote plasma region to generate plasma effluents of the first fluorine-containing precursor and the sulfur-containing precursor. The methods may include flowing the plasma effluents into a processing region of the semiconductor processing chamber. A substrate may be positioned within the processing region. The substrate may include a trench formed through stacked layers including alternating layers of silicon nitride and silicon oxide. The methods may include isotropically etching the layers of silicon nitride while substantially maintaining the silicon oxide.