In the past year, several researchers have reported on methods for extracting the true dopant profile from spreading resistance measurements. This paper reports on some theoretical aspects of the 1D Poisson analysis used in these methods. Linear perturbation analysis is used to show the origin of noise amplification when calculating the dopant profile from the measured carrier profile. Perturbations on model data are used to demonstrate the robustness and accuracy of the general noise reduction method proposed by Mathur and Thurgate, without making anyaprioriassumptions about the functional form of the dopant profile. This method successfully extracts the surface dopant profile for low‐doped ultrashallow junctions for which the on‐bevel electrical junction falls outside the sample.