New divided-source structure to eliminate instability of threshold voltage in p-channel flash memory using channel hot-hole-induced-hot-electron programming

A divided source structure for p-channel flash memory is introduced to eliminate the threshold voltage instability during operation. The instability comes from the strong hot electron gate current of unselected cells having been programmed. The unselected cells will suffer from undesired programming, which creates an undesired leakage of unselected cells during the read operation. The proposed structure enables the source of unselected cells to be raised up to -3 V, which inhibits the channel hot electron generation efficiently due to reduction of the lateral field. Thus stability of the threshold voltage is achieved.