A silicon micromachined heat sink is presented. The device uses liquid cooling in microchannels to remove high heat fluxes. Deep reactive ion etching and multiple wafer bonding is employed to fabricate high aspect ratio, enhanced heat transfer surfaces and a flow channel network that enhances cooling efficiency and minimizes the pressure drop across the device. Experimental test results are presented. Tests to date indicate that up to 76.5 W/cm2 may be removed by the heat sink based on a 100°C electronic device temperature.