Spectroscopic ellipsometry was used to determine the permittivity of metals. A 200-nm-thick film was deposited on the glass substrate to eliminate the reflection effect from the substrate. To measure the permittivity over a wide bandwidth, UV-visible spectroscopic ellipsometry (from 200 nm to 1000 nm) and mid-infrared spectroscopic ellipsometry (1700 nm to 20000 nm) were used. After determining the optimal permittivity for each measurement result using the Drude-Lorenz model, the results of both UV-VIS and MIR measurements were concatenated to determine the optimal parameters using the single Drude-Lorenz model and the least-squares method. The following equation defines the used the Drude-Lorenz model for analysis in this study: