We report on the electric field modulation of superconductivity in thin-film field-effect transistors based on lanthanum-doped strontium titanate (La:STO) channels with n-type channel carrier densities in the range of 3-7 X 10(19) cm(-3) and thickness in the range of 75-150 nm and undoped strontium titanate (STO) gate insulation. Electric field tuning of normal state resistance and channel critical current are observed in both enhancement and depletion modes. Gate modulation of superconductivity at finite frequency has been observed and is consistent with a small-signal analysis. (c) 2005 Published by Elsevier B.V.