Focused ion beam (FIB) processes have been developed for Y–Ba–Cu–O superconductor films. A Y–Cu liquid metal ion source has been fabricated, using a Y67 –Cu33 eutectic alloy as the ion source. As‐sputtered Y–Ba–Cu–O film etch rate ratios to GaAs(100) and Si(100) substrates are 0.28 and 1.4 for 130‐keV Au+ FIB ion etching, respectively. Y–Ba–Cu–O submicron patterns have been demonstrated by using FIB lithography and Cl2 reactive ion beam etching. Moreover, a Y–Ba–Cu–O superconducting line with 4‐μm linewidth has been fabricated by annealing an as‐sputtered Y–Ba–Cu–O line pattern. Tc control of Y–Ba–Cu–O film has been achieved by 200‐keV Ne+, using conventional ion implantation and 300 keV Si++ FIB ion implantation.