There have been demands for transparent electrode materials and magnetic materials, each having a wide range of applications. In view of the situations, a novel functional device and a method for forming an oxide material are provided. A functional device includes an AlxGayInzN layer (wherein 0≦x≦1, 0≦y≦1, and 0≦z≦1) and an oxide material layer composed of a metal oxide and formed on the AlxGayInzN layer. The metal oxide may be TiO2. The present invention provides a functional device that includes a group III nitride layer having excellent physical and chemical properties and a film integrally formed thereon. The film reflects less light at the interface and has chemical resistance and high durability.