Spaced apart conductive strips are provided in a first and third of three layers covering a semiconductor substrate. Magnetic core material is included in the second layer so as to be interposed between the conductive strips of the first and second layers. The first and second layers are joined at suitable points so that their respective conductive strips combine to form a helical electrical path which spirals about a core portion of the magnetic material in the second layer. The second layer can be patterned to define a toroidal magnetic path and/or to define a path including a magnetic gap. The armature of an electromechanical relay can be formed within the optional gap by depositing magnetic armature material to partially overlap a sacrificial support base. When the sacrificial support base is etched away, it leaves the overlying armature material free to move.