The effect of high frequency (1 MHz) acoustic agitation (megasonic agitation) on development of electron beam exposed poly(methylmethacrylate) (PMMA) nanostructures is investigated. Test patterns consisting of dense holes, isolated lines, and gratings with high aspect ratios have been used. Compared to conventional dip development, the sensitivity of the development process is increased and the homogeneity of nanopatterns is improved considerably. Furthermore, experiments towards ultimate aspect ratios and resolution of PMMA in the range of 2 - 3 ran with megasonically assisted development have been carried out. The physical mechanisms for the observed enhanced development performance which is particularly attractive for nanostructuring are discussed. (c) 2006 American Vacuum Society.