We propose a new process for fabrication of an ultrafine anisotropic SiO2 mask, successfully combining electron beam (EB) lithography and SF6 reactive ion beam etching using an Al lift-off. SiO2 etching had a high selectivity of 50 over Al with an SF6 pressure of 0.9 mTorr and an ion energy of 300 V, because formation of AlF3 near the surface prevented the etching of Al. EB patterns were precisely transferred to the SiO2 mask with a vertical wall. Using this process, lines with widths of 70 nm and dot arrays composed of columns with diameters of 70 nm were realized.