Compact multi-state ROM cell

摘要

A compact, multi-state field effect transistor (FET) cell having a gate with edge portions of a different conductivity type than a central portion of the gate. Both the edge portions and the central portion extend from the source to the drain of the multi-state FET device. This device would have two different threshold voltages (VT), one where the central portion would turn on first, followed by the edges for the entire gate width to be active to give a second level of current flow. Such devices would be useful in building very compact or high density multi-state read-only-memories (ROMs).