This work presents a comprehensive investigation on the modeling and characterization of the direct-tunneling (DT) current in ultrathin-gate dielectric film based on the classical model equation. Merit of replacement, which takes both the capacitance gain and the DT current suppression into consideration, was introduced to have a better comparison of different gate dielectric materials. A simple approach for modeling the dual-layer dielectric film is also developed. The tunneling characteristics of a dual-layer stack are modeled with an effective barrier and an effective thickness. The simple approach is particularly useful for device designs and process evaluation. (c) 2006 American Vacuum Society.