A method to extract gate to source/drain and overlap capacitances is disclosed. A first capacitance of a first test key having a reference structure and a second capacitance of a second test key having a novel structure are measured. The second test key may comprise at least a gate formed on an insulation structure, at least a contact formed on the insulation structure aside, and a metal layer formed on the contact. Another embodiment of the second test key may comprise at least a gate formed on the semiconductor substrate, a contact formed aside, and a metal layer formed on the contact. Further another embodiment uses a test key comprising at least an elongated gate and an elongated doping region aside, and only one or a few contacts are formed on an end portion of the elongated doping region.