A CMOS integrated circuit includes a Hall sensor having a Hall plate formed in a first isolation layer which is formed concurrently with a second isolation layer under a MOS transistor. A first shallow well with a conductivity type opposite from the first isolation layer is formed over, and extending to, the Hall plate. The first shallow well is formed concurrently with a second shallow well under the MOS transistor. The Hall sensor may be a horizontal Hall sensor for sensing magnetic fields oriented perpendicular to the top surface of the substrate of the integrated circuit, or may be a vertical Hall sensor for sensing magnetic fields oriented parallel to the top surface of the substrate of the integrated circuit.