  Current portable memory device relies heavily on flash memory technology for
its implementation. New generation of non-volatile memory is likely to replace
floating gates, charge-trapping memory currently still suffering from
inadequate retention performance and slow programming speeds as well as small
memory window. In contrast, the use of HfO$_2$/Al$_2$O$_3$ stacked high-k
materials has substantially increased the memory window of memory devices, with
a 63% increase relative to pure HfO$_2$ materials. The current goal of up to
80% retention characteristics over a ten-year period has been achieved by
adjusting the deposition ratio or dopant material. Process conditions can
continue to be investigated in the future to reduce charge loss while
maintaining the increased memory window.
