A bandgap engineered SONOS (BE-SONOS)  using Al2O3 top blocking layer and metal gate (MA BE-SONOS) is proposed to provide very fast erase speed without erase saturation. Compared with MANOS  using a thick (4.5 nm) tunnel oxide, MA BE-SONOS shows dramatically faster erase speed, owing to the help of bandgap engineered ONO barrier that facilitates hole tunneling. Compared with BE-SONOS using P+-poly gate and top oxide, MA BE-SONOS does not show any erase saturation, owing to the help of metal gate and Al 2O3 blocking layer, which greatly reduce gate injection during erase. Very large memory window (>7V) can be achieved with excellent data retention. MA BE-SONOS overcomes the erase difficulty in SONOS-type devices, and is highly potential in the future flash memory technology.