We have developed a patterning technique to define ultrafine lines with high density and good uniformity using sidewall structures. Approximately 50 nm multiple lines, which have 70 nm as the narrowest space between the lines, are defined by the pattern multiplication technique. Linewidths are measured at several points on wafers and their uniformity is verified. These patterns have a good uniformity (deviation 2.26-4.35 nm). Also, die-to-die uniformity is very good. The advantage of this technique is the easy control (using sidewall width control) of the line and space of patterns. This technique is free from the proximity effect because of the process using a sidewall hard mask. Thus. it is expected that the pattern multiplication technique can be applied to fabricate single electron devices, quantum devices, and other nanoscale devices. (C) 2003 American Vacuum Society.