The structural and magnetic properties of CoO/Co nanocaps prepared by electron beam evaporation technique as a function of Cothickness [ultra-thin (10 nm) and thick (100 nm)] films are presented. These films were deposited on PS (Polystyrene) nanospheres (600nm diameter) self-assembledon Si (100) substrate through nanosphere lithography. For a comparative study, these films were also deposited on plane Si substrateunder same deposition conditions.While Scanning electron microscopy showed the morphology and uniform distribution of nanospheres, corresponding roughness and thickness of the thin films on bare substrate were calculated using X-ray reflectivity technique. in which changes in XRR oscillations with film thickness have been observed. Magnetic properties were investigated using magneto optical Kerr effectwhich show enhancement in coercivity with increase in film thickness. The results are interpreted in terms of nanosphere curvature resulting in the variation in film thickness across this curvature.