The diagnostic of inner plasma parameters during industrial processing is still a challenge. The planar multipole resonance probe (pMRP) is a promising candidate for this purpose. It can be integrated into the chamber wall and is thus minimally invasive. For the pMRP it was possible to derive an analytic solution of the admittance based on idealizations and an electrostatic approximation. However, electromagnetic simulations of the real pMRP with CST Microwave Studio showed meaningful differences between the obtained resonance frequencies. In this work, it will be shown with simulations in Comsol Multiphysics, that the main difference between the resonances of the ideal and the real pMRP is caused by the thickness of the insulation between the electrodes and the chamber wall.