The disclosure relates to integrated circuits and methods of manufacture. A method involves forming a first set of one or more circuit layers on a semiconductor substrate, placing at least one prefabricated layer portion onto the first set of circuit layers to form a component, and forming a second set of one or more circuit layers over the first set of circuit layers and the at least prefabricated layer portion. The prefabricated layer portion may be a magnetic layer portion placed to form a magnetic component such as a magnetic core of an inductor or transformer. The method may also comprise forming the prefabricated layer portion.