The effects of residual oxides formed on polycrystalline Si and active Si on the formation of CoSi2 and its sheet resistance for 0.18 mm complementary metal oxide semiconductors (CMOS) have been investigated considering its formation regions and process parameters such as polycrystalline structure and grain size, kinds of dopant, and integration schemes. Having a columnar-type polycrystalline Si, strong linewidth dependence of the sheet resistance was observed in the p+ polycrystalline regions but not in the n+ polycrystalline regions or the n+/p+ diffusion regions. The same results were also observed when a granular-type polycrystalline Si was deposited as a gate material. The sheet resistance of CoSi2 in the p+ polycrystalline regions having a granular-type polycrystalline Si is higher than that of a columnar-type polycrystalline Si at all gate lengths. These results were found to be due to oxide that resided on the surface of polycrystalline Si in the p+ polycrystalline regions and due to the larger area of grain boundary. An alternative integration has no linewidth dependence in any silicided regions down to 0.15 mum gate length through removing the rapid thermal oxide (RTO) completely, which was used to block the dopants' out-diffusion from the source/drain and gate during the source/drain annealing that was processed before the cobalt deposition. Confirmation of these results was processed through lengthening the time of the diluted HF precleaning step to remove the RTO completely. (C) 2004 The Electrochemical Society.