A method and device for determining, in a non-destructive way, at least the active carrier profile from an unknown semiconductor substrate are disclosed. In one aspect, the method comprises generating 2 m independent measurement values from the m reflected signals and correlating these 2 m measurement values with 2 m independent carrier profile values. The method further comprises generating additional 2 m measurement values to allow determining the active carrier profile and a second parameter profile by correlating the 4 m measurement values with the 4 m profile values. The method further comprises generating a total of 2 m[n.k] measurement values to allow determining [n.k] independent material parameter depth profiles, each material parameter profile having m points.