Planar metal-ferroelectric-superconductor field effect transistors (MFS-FETs) have been fabricated on SrTiO 3 (100) substrates. The FET has the structure of Al/BaTiO 3 (BTO)/(Y 0.6 Pr 0.4 )Ba 2 Cu 3 O y (YPBCO), where the oxide layers are grown heteroepitaxially by ArF excimer laser deposition using an in situ metal mask changing system. The relative dielectric constant (e r ) of BTO is 200 at 77 K, and the ferroelectric field effects at low temperature have been measured. The source-drain current (I SD ) is enhanced 28% by applying negative gate voltage of -1.5 V. These results indicate that the Al/BTO/YPBCO structures are favorable for use in the superconducting FET.