Thin-film inductor device

A thin-film inductor device, comprising:

• a substrate which is made of an electrically insulating material, and which has opposite upper and lower surfaces;
• a first coil unit which is made of an electrically conductive material, and which includes
• a first upper coil formed on said upper surface of said substrate,
• a first lower coil formed on said lower surface of said substrate, and
• two first electrodes spaced apart from each other, and electrically connecting to said first upper and lower coils, respectively;
• a second coil unit which is made of an electrically conductive material, and which includes
• a second upper coil formed on said upper surface of said substrate, said second upper coil and said first upper coil being disposed spacedly and arranged by bifilar winding,
• a second lower coil formed on said lower surface of said substrate, said second lower coil and said first lower coil being disposed spacedly and arranged by bifilar winding, and
• two second electrodes spaced apart from each other, and electrically connecting to said second upper and lower coils, respectively;
• and
• an inductance-enhancing structure which encapsulates said substrate, said first coil unit, and said second coil unit such that two terminal parts of each of said first electrodes and said second electrodes are exposed for external electrical connection.