Development of low dielectric constant ferroelectric materials for the ferroelectric memory field effect transistor

In this paper we discuss ferroelectric materials suitable for a metal-ferroelectric-metal-insulator-semiconductor feild effect transistor (MFMIS FET). It is important for a ferroelectric material to have a low dielectric constant to enable the application of sufficient electric field to a ferroelectric layer. Films of Sr2Nb2O7 and Sr-2(Ta1-xNbx)(2)O-7 were prepared by the sol-gel method on Pt/IrO2 electrodes for an MFMIS FET. The ferroelectricities of Sr-2(Ta1-xNbx)(2)O-7 films were confirmed to be in the range of x = 0.1-0.3. In the case of x = 0.3, the largest remanent polarization was obtained in the hysteresis loop. The values of the remanent polarization and the coercive field are 0.5 mu C/cm(2) and 44kV/cm, respectively. The film has a low dielectric constant (epsilon(r) = 53). The characteristics of Sr-2(Ta1-xNbx)(2)O-7 thin films are suitable for MFMIS FET.