The behaviour of nickel (Ni) contamination in silicon-on-insulator (SOI) wafers has been characterized by the Kelvin method combined with surface photovoltage (SPV) measurements. In order to characterize the SOI wafers contaminated with Ni atoms, we used the “patterned” separation by implanted oxygen (SIMOX) wafers with partially no buried oxide (BOX) region, which acts as an opening of the top-Si layer to the substrate. It is found that the smaller size of patterned SIMOX area help the gettering of Ni atoms in the top-Si layer through the openings to the substrate because of its shorter lateral migration distance for Ni atoms. In addition, it is found that the intensity of SPV for the SIMOX areas increases with increasing a line width of the openings because of its wider vertical diffusion path away from the top-Si layer toward the substrate. These results clearly suggest that the Ni atoms in the SOI layer even with the underneath BOX layer can diffuse laterally and escape to the bulk region through the BOX-less region.