The characterization of modern interconnect architectures and materials for ICs requires extensive interline capacitance measurements at low frequencies (100 kHz-1 MHz) for evaluating the dielectric constant k of the insulating materials, which separate the conductive wires in the same metal level. The type of structure used for this purpose often features a considerable length. This characteristic can result in a frequency dependence of the measured capacitance value that can easily lead to under-estimate the k value of the insulator. The aim of this paper is to show and explain the frequency dependence by the study and the modeling of the typical interline capacitance structure. The results of this study lead to determining a design parameter and a measurement procedure to circumvent the problem.