We have developed a three-level-based PMMA/Ti/Pt resist system for the fabrication of high T c superconducting structures with lateral dimensions in the 100nm region. The degradation of superconductivity after substractive sub-μ patterning of high T c YBCO-films is minimized. In order to perform conductance measurements, where large contact pads have to be attached to submicron bridges, high resolution electron beam lithography has been combined with optical lithography. Thereby, the YBCO-film remains protected by the bottom platinium layer until the final ion milling step. As a result, bridges with a linewidth down to 150 – 200nm and up to several μm in length have been fabricated, which retain their superconductivity even without oxygen reloading.