This paper presents the benchmark test results on the symmetry and continuity characteristics between BSIM4 from Berkeley and ULTRA-BULK from Peking University. It is shown that the industry standard model BSIM4 has a series of the shortcomings of the continuity and symmetry, such as the charge, high-order current derivatives, and the trans-capacitances while the latest advanced surface-potential based MOSFET compact model, ULTRA-BULK, demonstrates all necessary continuity and symmetry characteristics, which are very important for analog and RF circuit design.
A surface potential-based model for undoped symmetric double-gate MOSFETs is derived by solving Poisson＇s equation to obtain the relationship between the surface potential and voltage in the channel region in a self-consistent way. The drain current expression is then obtained from Pao-Sah＇s double integral. The model consists of one set of surface potential equations,and the analytic drain current can be evaluated from the surface potential at the source and drain ends. It is demonstrated that the model is valid for all operation regions of the double-gate MOSFETs and without any need for simplification （e. g., by using the charge sheet assumption） or auxiliary fitting functions. The model has been verified by extensive comparisons with 2D numerical simulation under different operation conditions with different geometries. The consistency between the model calculation and numerical simulation demonstrates the accuracy of the model.
