The method for determining the thickness of a dielectric layer according to the invention comprises the step of providing an electrically conductive body (11) having a dielectric layer (13) which is separated from the electrically conductive body (11) by at least a further dielectric layer (3) and a surface (15) of which is exposed. Onto the exposed surface (15) an electric charge is deposited, thereby inducing an electric potential difference between the exposed surface (15) and the electrically conductive body (11). An electrical parameter relating to the electric potential difference is determined and a measurement is performed to obtain additional measurement data relating to the thickness of the dielectric layer (13) and/or to the thickness of the further dielectric layer (3). In this way the thickness of the dielectric layer (13) and/or of the further dielectric layer (3) is determined. The method of manufacturing an electric device (100) comprises this method for determining the thickness of a dielectric layer. The apparatus (10) for determining the thickness of a dielectric layer is arranged to execute this method.