We have investigated the effect of electric field on the magnetization in La0.2Ca0.3MnO3 (LCMO) ultrathin film (-10 nm) by using it as the semiconductor channel material of a prototypical field effect device and SiO2 as dielectric gate. The direct magnetization measurements confirm the formation of a large ferromagnetic phase with the increase in the negative applied gate voltage. We have also shown that a large electroresistance (ER) of similar to 78% with V-g = 8 V can obtained in LCMO by using a dielectric gate by reducing the thickness of the LCMO channel. (C) 2016 Elsevier B.V. All rights reserved.