We show that the electric polarization at the interface with ultrathin
superconducting (S) films sandwiched between ferroelectric (FE) layers allows
achievement of substantially stronger modulation of inner carrier density and
superconducting transition temperature as compared to FE-S bilayers typically
used in superconducting FETs. We find that not only the larger penetration
depths but also the pairing symmetry should be responsible for the fact that
the electric field effect in high temperature superconductors is much stronger
than in conventional systems. Discussing the advantages of multilayers, we
propose a novel design concept for superconducting electric field-effect
transistors based on ferroelectric films.Comment: 5 pages RevTex4, 6 figure