Non-volatile memories and methods of fabrication thereof are described. In one embodiment, a method of fabricating a semiconductor device includes forming an oxide layer over a semiconductor substrate, and exposing the oxide layer to a first nitridation step to form a first nitrogen rich region. The first nitrogen rich region is disposed adjacent an interface between the oxide layer and the semiconductor substrate. After the first nitridation step, the oxide layer is exposed to a second nitridation step to form a second nitrogen rich region. A first gate electrode is formed on the oxide layer, wherein the second nitrogen rich region is disposed adjacent an interface between the oxide layer and the first gate electrode.