Modeling of MOS transistors with nonrectangular-gate geometries

The dc electrical characteristics of MOS transistors with nonrectangular-gate geometries are investigated. Closed-form analytical expressions relating the terminal characteristics to the geometric parameters are presented for several gate geometries including the trapezoid, "V," "L," and annulus. Experimental results based upon a specially fabricated NMOS test bar containing these nonrectangular devices are presented. A comparison of the theoretical and experimental results is made which shows close agreement.