Access time independent of physical location of data. Non-uniform access time. More difficult to build. Typically, the single module version shown previously is good up to about 256Kbits. This is accomplished through a floating gate.
Hot electrons traverse first oxide and get trapped on floating gate, leaving it negatively charged.
The method of erasing is the main differentiating factor between the various classes of reprogrammable nonvolatile memories. UV light renders oxide slightly conductive. Limited number of programming cycles - about 1000. Very dense - single transistor functions as both the programming and access device. Very thin oxide allows electrons to flow to and from the gate via Fowler-Nordheim tunneling.