This work addresses the use of HfO 2 as trapping layer in TaN/Al 2 O 3 /HfO 2 /SiO 2 /Si (TAHOS) stacks for scaled non-volatile memories, by a complete characterization of the physical properties as a function of thermal budget and film thickness and of the program characteristics, with the aim of a benchmarking with the conventional Si 3 N 4 (TANOS). The TAHOS stack withstands high temperature budget (>1000°C) and shows similar program speed with respect to TANOS devices, thus revealing similar electron injection conditions. Moreover, the high dielectric constant of HfO 2 allows for an efficient EOT scaling and/or a large physical thickness for an improved trapping efficiency. Modeling of program transients contributed to the understanding of the trapping in TANOS/TAHOS devices and to the identification of physical processes possibly limiting the gate stack scaling.