A semiconductor device including a substrate, a semiconductor element formed on the substrate, a terminal formed on the substrate and electrically connected to the semiconductor element, and a protective resistor formed on the substrate and electrically connected between the semiconductor element and the terminal. The resistor is composed of a ferromagnetic magnetoresistive material including Ni alloy. The device may be extended to detect magnetism by adding a magnetoresistive element composed of a ferromagnetic magnetoresistive material including the same Ni alloy as for the protective resistor and deposited at the same time. The device is superior in an anti-noise characteristic and is integrated. Furthermore, the device for detecting magnetism is formed with a lower cost.