Abstract: A method for determining an end point in a chemical mechanical polishing process by utilizing a dual wavelength interference technique and an apparatus for carrying out such method are provided. In the method, a rotating platen that is equipped with a laser generating source capable of generating laser emissions in two different wavelengths is utilized such that a dual wavelength interference pattern may be received by a laser detector and a greatly expanded period between cycles in a resulting dual wavelength interference pattern may be utilized to determine the end point for material removal in a significantly larger thickness of material. The present invention novel method and apparatus can be utilized not only in monitoring the end point of CMP polishing of a thin oxide layer such as ILD or STI, but also in material removal of larger thickness such as in the planarization process of an IMD layer.