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Reliability properties of bandgap engineered SONOS (BE-SONOS) (Lue et al., 2005) are extensively studied. First, the erase mechanism of BE-SONOS is confirmed as substrate hole tunneling through the ultra-thin ONO tunneling dielectric. Next, very long-term (>3,000 hours) high-temperature baking data (from 150 to 250degC) for various programmed/erased states and cycling history are collected and analyzed for a thorough understanding of the retention property. By transforming retention data (VFB-time) into de-trapping current (J) and modeling its dependence on electric field and temperature, the long-term retention of various programmed states are consistently and accurately predicted. This modeling technique avoids the ambiguity of the common Arrhenius plot, and is useful for developing other predictive models too. We have shown that BE-SONOS surpasses the 10-year 85degC storage criterion for Flash memory applications