A transformer includes a silicon substrate, a plurality of metal layers and a plurality of insulating layers laminated on the silicon substrate, a bottom winding of a metal contacting a first metal layer and a second metal layer of the plurality of metal layers, a first insulating layer on the bottom winding, a core on the first insulating layer, a second insulating layer on the core, a top winding of the metal that extends around the core and a portion of the second insulating layer, and a third insulating layer on the top winding. At least one of the top winding and the bottom winding is thicker than each of the plurality of metal layers.