Purpose – In this paper, we propose a new 3D substrate extraction technique with the associated interconnect Methodology approach - It is adapted from methods of transmission lines or Green kernels, but in the volume. Findings - The substrate and interconnect coupling , with losses in integrated circuits; can be analyzed by this technique. We implement our algorithms in MATLAB, which can extract the impedances between all buried contacts, of varying forms, or/and via . The proposed model is verified for Z parameters in our simulations, by comparing with a finite elements analysis and tested with different parameters: frequency, distance between contacts/TSV, and the properties of the silicon substrate. Originality/value - The models are dedicated to 3D, and the algorithms are run in the reciprocal space, using Direct Cosine Transforms, for the sake of accuracy and fast calculations. We believe that these algorithm 3D are efficient and easy to use.