It has been known that the chamber aspect ratio (length/radius) played a significant role in defining ion flux and neutral flux uniformity (including passivaiton distribution) across the wafer in an inductively coupled plasma source. This paper will present a detailed study of silicon etch rate and CD uniformity as a function of chamber aspect ratio. Process parameters such as pressure, power and chemistry dependence on etch rate and CD uniformity are systematically compared under different chamber body length. A series of plasma modeling and gas flow modeling using a 2-D axisymmetrical fluid model are conducted and compared with the experimental data. The results show that an optimal chamber aspect ratio design requires careful balancing of plasma source uniformity as well as by-products distribution across the wafer in order to meet the overall stringent gate patterning etch requirements.