is assumed for purposes of the present discussion that the circuit portion 17 is a single semiconductor circuit component such as a diode or a transistor however the circuit portion 17 could alternatively include two or more circuit components a layer 21 of an electrically insulating material is provided on top of the substrate 12 so as to cover at least part of the semiconductor portion 16 in fig1 the insulating layer 21 is made from silicon dioxide but it could alternatively be made from any other suitable insulating material a further circuit portion 22 is shown diagrammatically and has one section which is on the insulating layer 21 and a further section which is on the surface of the substrate 12 the semiconductor portion 16 of the substrate 12 has a degree of electric conductivity and the insulating layer 21 provides electrical insulation between the circuit portion 22 and the semiconductor portion 16 outside the semiconductor portion 16 the silicon substrate 12 is electrically non conductive and thus the circuit portion 22 has a section which is provided directly on the top surface of the substrate 12 the circuit portion 22 includes one or more non semiconductor circuit components sometimes known as passive components such as resistors capacitors and or inductors the passive components may for example form a matching network the circuit portion 22 is electrically.