Abstract: There is provided a method of processing a substrate comprising an ONO stack in which a silicon oxide layer and a silicon nitride layer are stacked alternately and repeatedly on the substrate. The method includes: (a) primarily dry-etching silicon nitride layers of the ONO stack; (b) producing oxygen radicals and processing silicon oxide layers of the ONO stack with the oxygen radicals; and (c) secondarily dry-etching the silicon nitride layers of the ONO stack.

Abstract: The present invention relates to a substrate processing method for selectively etching a silicon nitride layer on a substrate on which silicon oxide layers and silicon nitride layers are alternately stacked, the method including plasma etching the silicon nitride layers using plasma of a plurality of gases, wherein the plurality of gases include a first gas containing fluorine excluding nitrogen trifluoride (NF3) and a second gas containing hydrogen, and the etch profile in the thickness direction of the silicon nitride layers is controlled by adjusting the atomic ratio of fluorine to hydrogen included in the plurality of gases.