Charge trapping flash memory devices using (HfO 2 ) 0.9 (Al 2 O 3 ) 0.1 as the charge trapping layer were fabricated, and the effect of post-annealing atmospheres (NH 3 and N 2 ) on its charge storage characteristics was investigated. It was found that NH 3 annealed memory device showed a larger memory window of 7.3 V and improved data retention even at 85 °C compared to N 2 annealed memory devices. The enhanced memory characteristics should be attributed to deep level bulk charge traps induced in the charge trapping layer by NH 3 annealing. In addition, the large conduction band offset value between tunneling layer and charge trapping layer also resulted in good retention performance.