A magnetic flux concentrator (MFC) structure comprises a substrate, a first metal layer disposed on or over the substrate, and a second metal layer disposed on or over the first metal layer. Each metal layer comprises (i) a first wire layer comprising first wires conducting electrical signals, and (ii) a first dielectric layer disposed on the first wire layer. A magnetic flux concentrator is disposed at least partially in the first metal layer, in the second metal layer, or in both the first and the second metal layers. The structure can comprise an electronic circuit or a magnetic sensor with sensing plates. The structure can comprise a transformer or an electromagnet with suitable control circuits. The magnetic flux concentrator can comprise a metal stress-reduction layer in the first or second wire layers and a core formed by electroplating the stress-reduction layer.