A three-dimensional integrated circuit apparatus includes a three-dimensional integrated circuit including a group of integrated double-layer microchannels (DLMC) and multi-layer microchannels (MLMC) with optimized thermal performance for the three-dimensional integrated circuit. A heat source can be uniformly distributed in each layer and can be conducted through the layers down to the substrate and up to a spreader and a heat sink, and eventually to ambient air through forced convective heat transfer above the heat sink and natural convective heat transfer under the substrate.