This article reports the fabrication of sub-10-nm Si lines by e-beam lithography and aqueous potassium hydroxide (KOH)-based etching. The fabrication technique provides both the high resolution and minimum linewidth fluctuation necessary for fabricating nano-scale Si structures. In e-beam lithography, the combination of high-resolution posi-type resist and hexyl acetate developer is effective in improving the resolution and in reducing pattern fluctuation. Resist lines less than 20 nm wide with a fluctuation less than 3 nm are obtained. When these lines, aligned in the (112) direction on a (110) Si wafer, are transferred to Si by KOH etching, Si lines with a rectangular cross section are obtained and linewidth fluctuation is reduced further because (111) planes are exposed as the sidewalls. In addition, 6-9 nm wide lines can be formed by additional etching using an alcohol/KOH solution. Photoluminescence spectra are obtained for sub-10-nm Si lines after slight oxidation.