Epitaxial multilayers, consisting of a PrBa2Cu3O7-x buffer layer, ultr
athin YBa2Cu3O7-x and SrTiO3, have been grown for application in elect
ric field effect devices. Different analytical techniques indicate a s
harp interface between the layers and good dielectric properties of th
e SrTiO3-layer. First measurements show clear modification of the supe
rconductor's current-voltage characteristics upon applying electric fi
elds of 0.1-1 MV/cm.