Long-term retention of SNOS nonvolatile memory devices

Long-term retention tests on thin oxide SNOS (silicon gate nitride oxide silicon) nonvolatile memory devices have shown that the charge storage characteristics of these devices do not follow a simple logarithmic decay as many theories predict. The measured threshold voltage decay shows a break in the slope of retention data for both the WRITTEN and ERASED states with smaller rates of charge loss per decade of time for longer times.