Most of the heat generated by a microprocessor comes from its cores, resulting in hotspots with exceptionally high heat flux. In contrast, the remaining processor area experiences significantly lower heat flux, leading to substantial temperature nonuniformity across the chip. An efficient heat sink must be capable of applying distinct cooling capacities specific to each zone. This study presents an energy-efficient heat sink design aimed at mitigating severe temperature variations in microprocessors. The design concept involves dividing the processor's hot surface into zones based on heat flux intensity and integrating different microstructures and materials into each respective zone for optimized thermal management. The proposed hybrid-composite design was developed by incorporating silicon microchannels for the low-heat-flux zone and diamond microfins for the highheat-flux zone. Integrating microfins (hybrid design) substantially enhances the solid-fluid interface area over the hotspot zone, while using diamond (composite design) dramatically improves heat conduction from the hotspot. Full heat sinks were modeled for conjugate heat transfer investigation. The thermo-hydraulic performance of hybrid-composite design was compared against that of simple, simple-composite, and hybrid designs. The hybrid-composite design demonstrated substantial enhancement in thermal performance compared to all the other designs, with a moderate rise in pumping power. In comparison to the simple microchannel design, the hybrid-composite design demonstrated a 66.0 % reduction in thermal resistance and a 74.3 % decrease in temperature nonuniformity. Additionally, the hybrid-composite design could effectively mitigate a hotspot heat flux of up to 2400 W/cm2 with only 8.6 % higher pumping power, while the simple microchannel design reached the maximum permissible temperature limit at 700 W/cm2.