We investigated the appropriate wet cleaning process for Co-Ti-Si compounds formed on top of cobalt disilicide made from Co/Ti deposition and two rapid thermal annealing (RTA). We employed three wet cleaning processes, WP1 ($H_2$SO$_4$ etchant), WP2 ($NH_4$OH etchant), and WP3 which execute sequentially WP1 and WP2 after the first RTA. All samples were cleaned with BOE etchant after the second RTA. We characterized the sheet resistance with process steps by a four-point probe, the microstructure evolution by a cross detail sectional transmission electron microscope, a Auger depth profiler, and a X-ray diffractometer (XRD). We confirmed WP3 wet cleaning process were the most suitable to remove CoTiSi layer selectively.