We report on techniques for fabricating 20‐nm scale ballistic electron devices and on techniques for imaging and characterizing these patterns in thin layers of poly(methylmethacrylate) (PMMA). A split‐gate fabrication approach with nanometer‐scale Schottky gates is used. Using a multiple layer PMMA resist technique, we have fabricated Au/Pd gates as narrow as 20 nm. In order to enhance the undercut profile a lower molecular weight PMMA is used as the bottom layer. We have also developed a resist stabilization technique which allows the viewing of 20 nm scale features in 0.1‐μm thick PMMA resist under high magnification in a scanning electron microscope. These techniques have been used to fabricate ballistic electron devices which demonstrate quantum interference effects.