Development of low dielectric constant ferroelectric materials for the ferroelectric memory feild [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 Sr 2 Nb 2 O 7 and Sr 2 (Ta 1- x Nb x ) 2 O 7 were prepared by the sol-gel method on Pt/IrO 2 electrodes for an MFMIS FET. The ferroelectricities of Sr 2 (Ta 1- x Nb x ) 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 µC/cm 2 and 44 kV/cm, respectively. The film has a low dielectric constant (ε r =53). The characteristics of Sr 2 (Ta 1- x Nb x ) 2 O 7 thin films are suitable for MFMIS FET.