The present disclosure provides a semiconductor device. The semiconductor device includes a semiconductor substrate having an integrated circuit (IC) device; an interconnect structure disposed on the semiconductor substrate and coupled with the IC device; and a transformer disposed on the semiconductor substrate and integrated in the interconnect structure. The transformer includes a first conductive feature; a second conductive feature inductively coupled with the first conductive feature; a third conductive feature electrically connected to the first conductive feature; and a fourth conductive feature electrically connected to the second conductive feature. The third and fourth conductive features are designed and configured to be capacitively coupled to increase a coupling coefficient of the transformer.