GENERALIZED SCALE LENGTH FOR 2-DIMENSIONAL EFFECTS IN MOSFETS

We derive a new scale length for two-dimensional (2-D) effects in MOSF ET's and discuss its significance. This derivation properly takes into account the difference in permittivity between the Si channel and the gate insulator, and thus permits an accurate understanding of the eff ects of using insufficiently scaled oxide or thicker higher permittivi ty gate insulators. The theory shows that the utility of higher dielec tric constant insulators decreases for epsilon/epsilon(o) > similar to 20, and that in no event should the insulator he thicker than the Si depletion depth. The approach is also applied to double-gated FET stru ctures, resulting in a new more general scale length formula for them, too.