We proposed models of subthreshold characteristics for deep nanoscale short channel asymmetric junctionless Double-Gate (DG) MOSFETs. Models were derived by solving 2-D Poisson's equation using variable separation technique. The subthreshold behavior with structure asymmetry such as different gate oxide thicknesses and different gate biases between the front-gate and back-gate can be exactly described. Design parameters such as body doping, body thickness and channel length were considered. The models were verified by comparing with device simulations' results. (C) 2013 Elsevier Ltd. All rights reserved.