Abstract: A high performance, on-chip transformer having interleaving primary and secondary windings to achieve higher coupling coefficient while providing desired impedance transformation is disclosed. The primary winding is formed of two or more parallel conductive winding paths or segments. The secondary winding is embedded within the parallel paths of the primary windings. The transformer primary and secondary spiral turns are joined together using underpass/overpass connections made by breaking open a portion of secondary and primary spiral. Also electrically conductive cross-over junctions are used to establish equal path length across the spiral turns of the primary winding to minimize the magnetic losses and thus the spiral resistance at RF. Further, vias and cross-over junctions are also used to series stack the windings of secondary in an in-out and up-down fashion to enhance secondary inductance and thus impedance transformation.