This paper proposes an analytical model for an asymmetric double-gate metal-oxide-semiconductor field-effect transistor (DG MOSFET) with varying gate-oxide thickness (t(ox)) and flat-band voltage (V-fb) in the subthreshold region. Since such variations cannot be completely avoided, the modeling of their behaviors is essential. The analytical model is developed by solving a 2D Poisson equation with a varying channel doping concentration (N-A). To solve the 2D Poisson equation of the asymmetric DG MOSFET, a perturbation method is used to separate the solution of the channel potential into basic and perturbed terms. Since the basic terms can be regarded as the equations derived from a general symmetric doped DG MOSFET, the conventional analytical model is adopted. In addition, a solution related to the perturbed terms for the asymmetric structures is obtained using Fourier series. Based on the obtained channel potential, the electrical characteristics of the drive current (I-DS) are expressed in the analytical model. The prediction of the electrical characteristics by the analytical model shows excellent agreement when compared with commercially available 2D numerical device simulation results with respect to not only t(ox) and V-fb variations but also channel length and N-A variations. (C) 2016 Elsevier Ltd. All rights reserved.