A memory cell comprises a multilayer gate heating structure formed over a channel
region between source and drain regions. The multilayer gate heating structure
comprises polysilicon and metal silicide layers stacked over a similarly shaped
gate oxide. When a programming voltage is applied across the metal silicide layer,
there is intense localized heating. The heating causes segregation of the channel
dopant atoms towards the source and drain regions, lowering the threshold voltage
of the device. The heating causes carrier activation in the polysilicon layer and
dopant penetration through the oxide layer into the channel region, thereby increasing
the threshold voltage of the device.