A coil inductor and buck voltage regulator incorporating the coil inductor are provided which can be fabricated on a microelectronic element such as a semiconductor chip, or on an interconnection element such as a semiconductor, glass or ceramic interposer element. When energized, the coil inductor has magnetic flux extending in a direction parallel to first and second opposed surfaces of the microelectronic or interconnection element, and whose peak magnetic flux is disposed between the first and second surfaces. In one example, the coil inductor can be formed by first conductive lines extending along the first surface of the microelectronic or interconnection element, second conductive lines extending along the second surface of the microelectronic or interconnection element, and a plurality of conductive vias, e.g., through silicon vias, extending in direction of a thickness of the microelectronic or interconnection element. A method of making the coil inductor is also provided.