The operating characteristics of flash memory devices with tunnel dielectrics comprising a hafnium oxynitride (HfOxNy) layer or a hafnium oxynitride/silicon dioxide (HfOxNy/SiO2) stack, annealed at various temperatures, were studied. The present work indicates that flash memory devices with a HfOxNy/SiO2 stack tunnel dielectric have a higher program/erase speed and better reliability than those with a single HfOx/N-y layer. The stack tunnel dielectric composed of a thick HfOxNy layer and a thin SiO2 layer exhibits an even better performance in the flash memory operation. In addition, devices with HfOxNy/SiO2 stack tunnel dielectrics annealed at 850 degrees C show the best performance in terms of the program/erase speed, charge retention, and read disturbance. (c) 2006 American Vacuum Society.