AN EFFECTIVE CHANNEL-LENGTH DETERMINATION METHOD FOR LDD MOSFETS

We propose a definition of MOSFET effective channel length (L(EFF)), t hat provides a method of determining L(EFF) as a constant, and externa l resistance (R(EXT)) virtually as a constant, even for lightly doped drain (LDD) transistors. A unified relationship between this L(EFF) an d MOSFET drive current (linear and saturation) that is common to a wid e range of drain structures was confirmed, Therefore, the L(EFF) is us eful, not only for compact analytical models, but also as an index of MOSFET performance applicable to both single drain and LDD devices, Th e dependence of the channel length on the source/drain structure was c larified by introducing the concept of local contribution to channel l ength, The L(EFF) varies,even if the metallurgical channel length is f ixed, depending on the design of the source/drain.