Scanning Spreading Resistance Microscopy electro-mechanical nanocontacts are nowadays well understood and numerous influent parameters have been identified (Bias, load, surface state of the sample, radius of curvature of the tip). Despite several simulation and modelization possibilities, calibration curves are required to ensure reliable electrical characterizations. In this paper, we bring, through nano-structural studies (Scanning Electron Microscopy, Transmission Electron Microscopy) of surface state of both SSRM tips and doped silicon surface a new understanding of tip-sample interaction during SSRM measurements. As a result of load, a nanometric residual amorphous silicon layer was observed which thickness depends on applied force and might be due to as well the plastic transformation (Si to β-tin phase) as plough-effect residues resulting from the tip indentation into the sample. It appears thus in a failure analysis process to find the best compromise between stable electrical SSRM response and sample/tip surface degradation.