A method for fabricating a silicon-oxide-nitride-oxide-silicon (SONOS) non-volatile memory cell, wherein the method comprises steps as following: a pad oxide layer and a first hard mask layer are sequentially formed on a substrate. The pad oxide layer and the first hard mask layer are then etched through to form an opening exposing a portion of the substrate. Subsequently, an oxide-nitride-oxide (ONO) structure with a size substantially less than or equal to the opening is formed to coincide with the portion of the substrate exposed from the opening.