A unified analytical continuous model, based on an approximate solution of Poisson's equation, is proposed for the current-voltage (I-V) characteristics of accumulation mode (junctionless FETs) and conventional inversion mode MOSFETs which have symmetric and asymmetric double-gate structures. As a unified model, it is applicable to both junctionless and conventional double-gate (DG) MOSFETs and also represents the I-V characteristics of the MOSFETs with symmetric and asymmetric cases. The model with symmetric and asymmetric gates accounts for body doping, body thickness, and front-gate and back-gate oxide thicknesses. The model is verified by comparing with TCAD simulation results and shows a good agreement. (C) 2012 Elsevier Ltd. All rights reserved.