Charge-trapping device structure of $SiO2∕SiN∕high-k$ dielectric $Al2O3$ for high-density flash memory

We present a device structure of $SiO2∕SiN∕Al2O3$ (SANOS). The use of a high-$k$ dielectric material, specially $Al2O3$⁠, in the blocking oxide concentrates the electric fields across the tunnel oxide and SiN, and releases it across the blocking oxide under program and erase mode. This effect leads to lower program and erase voltage as well as faster erase speed than the conventional $SiO2∕SiN∕SiO2$ (SONOS) device. Moreover, it is shown that the fast erase operation is performed even at a thicker tunnel oxide over $30Å$ where the hole direct tunneling current through the tunnel oxide is reduced significantly and thus the SANOS device has the excellent bake retention.