The role of Al2O3 in MANOS device is critically examined, and we conclude that its primary function is to reduce gate injection during erase operation. By itself, Al2O3 cannot stop charge leakage from the charge-trapping nitride layer. Furthermore, Al 2O3 provides no magic during the erase operation, and MANOS erases very slowly through charge de-trapping. BE-SONOS , with the band engineered ONO tunneling layers, provides efficient channel hole injection for erase. BE-MANOS  should be an ideal combination with fast erase and good reliability. However, it shows poor data retention. By inserting a SiO 2 buffer layer between Al2O3 and the SiN storage layer, the oxide-buffered BE-MANOS shows good performance and good reliability. The EOT scalability is also investigated.