A foldable polymer-based coil structure and a method for fabricating the same are disclosed. The coil structure has metal wirings and interconnections between the wirings. The wirings and connections are embedded by a polymer. The coil structure is foldable in two or more layers. In the folded condition, coils of one layer overlap the coils of another layer. A stackable structure and jigs for aligning the foldable and stackable structures are also disclosed.