Spreading resistance in submicron MOSFET's

The spreading resistance due to current crowding at the end-points of an FET channel is investigated. An analytic expression is derived giving this resistance as function of a few parameters. Two-dimensional numerical simulations, using finite-element techniques, confirm the accuracy of the simple analytical approach. For short channel devices the current crowding effect is found to give a nonnegligible contribution to the total source resistance. In order to optimize the FET performance, the geometry and conductivity of the source/drain regions must be carefully designed, trading off short channel effect and transconductance degradation.