In this paper, a fully-integrated buck converter using packaging inductors and MIM(Metal-Insulator-Metal) capacitors is presented. Buck converter is designed using parasitic inductors of the bonding wires and the lead frames in the package and process capacitors for reducing size and cost. The chip has been fabricated with a 0.13µm CMOS process. The switching frequency is 50MHz, input voltage is 3.3V, regulation voltage is about 2V, maximum efficiency is 68.7% of maximum value.