Abstract: Microchannels are effective heat sinks for integrated electronic circuits. However, it remains unclear what form of channels will be most effective in improving the overall performance of microchannel heat sinks. The effect of channel geometry on overall performance was studied to understand the fluid flow and heat transfer characteristics of microchannel heat sinks having groove sidewalls. Five types of silicon-based microchannel heat sinks were designed, and the periodic grooves arranged on channel sidewalls were rectangular, triangular, trapezoidal, water-droplet, and semicircular in shape. A three-dimensional computational fluid dynamics model was developed, validated, and used to optimize the geometric structure. Comparisons were made between different groove shapes in order to determine the optimum structure. The results indicated that the overall performance can be greatly improved by arranging grooves on channel sidewalls. The significant improvement of overall performance can be achieved with all the groove shapes except rectangles. When the Reynolds number falls within the range from 194 to 610, triangles are the optimum groove structure in terms of the level of the maximum heat transfer performance improvement, but with a significant increase in pressure drop. Water-droplet shaped grooves offer many advantages and improvements that make them the preferred choice for the development of microchannel heat sinks. They offer significant advantages as an effective heat transfer enhancement structure at higher Reynolds numbers, and allow for the lowest pressure drop at lower Reynolds numbers due to the vortexes formed inside the grooves.