A method for measuring thickness variations in a first layer of a multilayer semiconductor structure, comprising: - acquiring, with an image acquisition system, an image of at least one zone of the surface of said structure, said image being obtained by reflecting a quasi-monochromatic light flux on said zone of the surface of said structure, - processing said acquired image so as to determine, from intensity variations of the light reflected by said zone of the surface, a map of the thickness variations of said first layer, said treatment comprising comparing the intensity of each pixel of the image with a predetermined calibration curve defining a relationship between the intensity of a pixel of the acquired image and a local thickness of the first layer, said calibration curve being determined for a given thickness of a second layer of the structure different from the first layer, wherein the wavelength of said quasi-monochromatic light flux is selected so as to correspond to a minimum of the sensitivity of the reflectivity with respect to said second layer, said sensitivity of the reflectivity with respect to a layer being equal to the ratio between: (i) the difference between the reflectivities of two multilayer structures for which the considered layer has a given thickness difference and (ii) said given thickness difference, the thicknesses of the other layers being identical in both multilayer structures, said method being characterized in that it further comprises: - measuring, in particular by ellipsometry, the thickness of the second layer in said at least one zone of the surface of the structure, - if said measured thickness is different from the thickness of the second layer considered in the calibration curve, applying a correction curve to the map of the thickness variations, wherein said correction curve defines, for said measured thickness of the second layer, a relationship between a thickness of the first layer and a correction factor to apply to the map of the thickness variations of the first layer, so as to determine a corrected map of thickness variations of the first layer. - acquiring, with an image acquisition system, an image of at least one zone of the surface of said structure, said image being obtained by reflecting a quasi-monochromatic light flux on said zone of the surface of said structure, - processing said acquired image so as to determine, from intensity variations of the light reflected by said zone of the surface, a map of the thickness variations of said first layer, said treatment comprising comparing the intensity of each pixel of the image with a predetermined calibration curve defining a relationship between the intensity of a pixel of the acquired image and a local thickness of the first layer, said calibration curve being determined for a given thickness of a second layer of the structure different from the first layer, wherein the wavelength of said quasi-monochromatic light flux is selected so as to correspond to a minimum of the sensitivity of the reflectivity with respect to said second layer, said sensitivity of the reflectivity with respect to a layer being equal to the ratio between: (i) the difference between the reflectivities of two multilayer structures for which the considered layer has a given thickness difference and (ii) said given thickness difference, the thicknesses of the other layers being identical in both multilayer structures, said method being characterized in that it further comprises: (i) the difference between the reflectivities of two multilayer structures for which the considered layer has a given thickness difference and (ii) said given thickness difference, - measuring, in particular by ellipsometry, the thickness of the second layer in said at least one zone of the surface of the structure, - if said measured thickness is different from the thickness of the second layer considered in the calibration curve, applying a correction curve to the map of the thickness variations, wherein said correction curve defines, for said measured thickness of the second layer, a relationship between a thickness of the first layer and a correction factor to apply to the map of the thickness variations of the first layer, so as to determine a corrected map of thickness variations of the first layer.