Flash transistors are used in memory devices. Their design is similar to that of MOSFETs with the main design difference being that they employ two gates rather than one in a planar MOSFET design (Figure 1). When a potential is applied to the control gate of the flash transistor, current flows between the source and drain. It differs from a conventional MOS device in that some electrons tunnel through the gate oxide to produce a permanent charge on the floating gate. The presence of this charge constitutes a logic “1” in the memory device. The charge on the floating gate can be removed by placing a negative potential on the control gate. When the floating gate has no charge, it constitutes a logic “0” in the memory device. Flash memory transistors are thus a fundamental component of most non-volatile memory devices, which are devices that maintain their charge when power is turned off.