Mobility bias-dependence is usually modeled by the effective electric field (Eeff). However, the influence of different device structures and quantum effect on the Eeff has not been thoroughly studied. In this paper, the Eeff in ultra-thin body (UTB) and double-gate (DG) MOSFETs is derived from the Poisson equation. Based on the Eeff, symmetric DG devices show higher mobility than asymmetric DG and UTB devices. Extensive simulations also show the quantum effect has no influence on the Eeff, from which the effective mobility (mueff) modeling with quantum consideration can be greatly simplified