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.