Multiple gate NVM cells with improved Fowler-Nordheim tunneling program and erase performances

Multiple gate tridimensional memory cells can have several additional advantages besides increased read current and excellent Ion/Ioff ratio, which are inherent in the multiple-gate transistor architecture. We show that tridimensional memory cells with rounded top geometry and SONOS storage stack strongly improve the Fowler-Nordheim tunneling program-erase performances because of an enhanced electric field effect and an increase of the cell coupling factor. Moreover, a remarkable enhancement of the tridimensional cell performances is expected if the blocking silicon oxide and the poly-silicon gate in the SONOS memory stack are replaced with a high-k dielectric and a high work-function metallic control gate.