In a non-volatile memory, the word lines (6) are closely spaced without the usual field oxide or trench isolation between adjacent word lines. In a virtual ground embodiment, the surface area of one cell may be reduced thereby to practically 2F2, F being the minimum photolithographically-limited process...http://www.google.de/patents/US6765261?utm_source=gb-gplus-sharePatent US6765261 - Semiconductor device comprising a non-volatile memory
