MONOS memory element

The use of metal-nitride-oxide-semiconductor structure as a storage element was reported by Szedon at the 1967 Device Research Conference. When such a structure is used as p-channel enhancement mode device, a positive gate voltage exceeding a certain critical value changes the device into depletion mode. Later when a negative gate voltage of the order of this critical voltage is applied, the device changes back to enhancement mode. This phenomenon has been explained as electron tunneling from the semiconductor through the oxide into the traps in the nitride with a positive gate bias, and from traps into the semiconductor with negative gate bias. This can be used as a nonvolatile memory element.