Measurement of thickness of layers of a circuit structure is obtained, where the thickness of the layers is measured using an optical critical dimension (OCD) measurement technique, and the layers includes a high-k layer and an interfacial layer. Measurement of thickness of the high-k layer is separately obtained, where the thickness of the high-k layer is measured using a separate measurement technique from the OCD measurement technique. The separate measurement technique provides greater decoupling, as compared to the OCD measurement technique, of a signal for thickness of the high-k layer from a signal for thickness of the interfacial layer of the layers. Characteristics of the circuit structure, such as a thickness of the interfacial layer, are ascertained using, in part, the separately obtained thickness measurement of the high-k layer.