Abstract: A heat-dissipating component including a heat-generating device such as a power semiconductor chip and a mounting structure is provided with coolant channels having a stair-stepped internal geometry that enhances cooling performance with both single-phase and two-phase cooling modes without unduly restricting coolant flow or significantly increasing manufacturing cost. The stair-stepped geometry enhances both single-phase and two-phase cooling modes by increasing the surface area of the channels, and further enhances the two-phase cooling mode by providing numerous high-quality bubble nucleation sites along the length of the channels. The stair-stepped channels are formed in the heat generating device and/or the mounting structure, and the stepped sidewalls may extend toward or away from the center of the channel.