A via is experimentally characterized by using highfrequency s-parameter measurements. Test patterns are designed and fabricated by using a package process. They are measured by using VNA (vector network analyzer) up to 25GHz. The parasitic effects due to access lines for on-wafer probing are deembedded. Then modeling the via as two equivalent circuits (Ttype and Pi-type), the circuit model parameters are determined. It is shown that the T-type circuit model has excellent agreement with the measured s-parameters.