Ferromagnetic semiconductors show a variety of spintronic properties, and most of which have not been accessible in conventional semiconductor devices and magnetic devices based on ferromagnetic metals. The devices based on ferromagnetic semiconductors can deal with semiconducting and magnetic functionalities simultaneously, and thus are being used to explore their potential application as well as physics involved in the device application. Since the operating temperature above room temperature is crucial for the application, a large effort is continuing to established ferromagnetic semiconductors with the Curie temperature well above room temperature. Our knowledge of the spintronic properties will be useful when appropriate ferromagnetic semiconductors in usage are once discovered. A number of new experimental findings have emerged and new ideas have embodied in the device operation, however, they are still in the elementary level from the technological point of view. In order to advance the area, we should clarify the architecture to realize the systems for special and even general purposes by making the most of the advantage of the devices based on ferromagnetic semiconductors.