Images of defects generated by immersing silicon wafer in slightly Cu-contaminated water of 500 ppt level were observed for the first time by using a highly sensitive defect detection system and coordinate linked atomic force microscopy. There are three types of surface defects: a protrusion-type defect 100-200 nm wide and 2-10 nm high, a shallow pit 100-200 nm wide and 5-10 nm deep, and a larger shallow pit 1 mu m wide and 2-8 nm deep. They are detected as laser beam scatters with sizes smaller than 90 nm-diam in spherical polystyrene-latex standard particle equivalence. From oxide breakdown characteristics of the wafer, these extremely small or shallow defects are believed to be potential origins which can deteriorate gate oxide integrity.