Radio-frequency magnetron cosputtering by setting an Al metal plate on an Al2O3 target is an effective method for fabricating Al-rich Al2O3 thin film, which is used as a charge storage layer for nonvolatile Al2O3 memory. The wet etching rate of the fabricated AlO film increases with Al content. The optical transmittance decreases when the Al content in AlO increases. Using rf magnetron cosputtering, the authors fabricated an Al2O3 film with an embedded Al-rich Al2O3 and investigated the charge trapping characteristics after a 30 min annealing at 550 degrees C. C-V characteristics indicate that the Al-rich Al2O3 structure is very stable after annealing. The charge trap density in Al-rich Al2O3 after annealing is much larger than that in stoichiometric Al2O3. (c) 2008 American Vacuum Society.