We report on the electrostatic modulation of superconductivity in ultrathin Nd1Ba2Cu3O7-δ films grown by RF magnetron sputtering using different field effect devices. In epitaxial ferroelectric Pb(Zr,Ti)O3 / Nd1Ba2Cu3O7-δ heterostructures, we have used the reversible ferroelectric polarization field to modulate the carrier density of the thin superconducting oxide films. In lithographically patterned structures, reversing the polarization field of the ferroelectric Pb(Zr,Ti)O3 layer allows large non-volatile modification of the critical temperature of the superconducting films to be obtained without introducing chemical or structural defects. We will also discuss reversible modifications of the superconducting properties in ultrathin Nd1Ba2Cu3O7-δ films using a novel field effect device based on a single crystal SrTiO3 dielectric gate insulator. With this device, the polarization can be precisely measured allowing the dependence of the superconducting critical temperature on the carrier concentration in the underdoped region of the phase diagram to be determined.