In this work we study the influence of the major focused ion beam operating parameters: ion chemical species, beam current, lens voltage and ion dose on the ultimate nanopatterning resolution. We propose a two-step process based on first ion milling of a SiO2 sacrificial layer and second SiO2 chemical etching for the fabrication of nanopatterns with ultimate size/density and ad libitum shape. Examples of resulting patterns are presented. (C) 2013 Elsevier B.V. All rights reserved.