The erase characteristics and mechanism of Al2O3 -nitride-oxide-silicon (MANOS) devices are extensively studied. We use transient analysis to transform the erase curve (VFB-time) into a J-E curve (J = transient current, E = field in the tunnel oxide) in order to understand the underlying physics. The measured erase current of MANOS is three orders of magnitude higher than that can be theoretically provided by substrate hole current. In addition, the erase current is very sensitive to the Al2O3 processing condition-also inconsistent with substrate hole injection model. Thus, we propose that MANOS erase occurs through an electron detrapping mechanism. We have further carried out a refill test and its results support the detrapping model. Our results suggest that the interfacial layer between Al2O3 and nitride is a key process that dominates the erase mechanism of MANOS.