The disclosure relates to a method of forming a hybrid circuit wherein two substrates, preferably though not necessarily, of diverse materials, are aligned on and secured to a glass plate by layers of polymer which are selectively etchable as to each other. The portion of the topmost polymer layer which is between the substrates is removed and the space therebetween is filled with an electrically insulating material which adheres to the substrates to form a surface between the substrates which is coplanar with the circuit containing surfaces of the substrates. Interconnects are then formed on the electrically insulating surface which extend onto both of the substrates. The remaining polymer layers are removed and the hybrid circuit which has been formed is then placed on a support to provide rigidity and, if necessary, heat sinking properties.