i A PHYSICAL IMPLEMENTATION WITH CUSTOM LOW POWER ...

Source
Gate Oxide
Control Gate
Oxide
Floating Gate
Channel Region
Tunnel Oxide
Drain
Figure 7-1: Structure of the FLOTOX Transistor
Control Gate
Floating Gate
Source Drain
Figure 7-2: Symbol of a FLOTOX transistor
Figure 7-2 shows the symbol of a FLOTOX transistor. The EEPROM FLOTOX
transistor has a Control Gate (CG) terminal, a Floating gate terminal (FG), a Source (S), a Drain
(D) and a Substrate (B) terminal. The FLOTOX transistor is fundamentally an n-channel double-
poly transistor in which the middle layer is floating and is called the floating gate [19]. The
FLOTOX EEPROM has a region where the oxide thickness is very low and is called the
tunneling window. The oxide at the tunneling window region is called the tunnel oxide. Figure
7-3 shows the IV characteristics of the FLOTOX transistor in its virgin state [19]. Virgin state of
the FLOTOX transistor is the state when the transistor has neither been erased nor written.
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