Sr2(Ta1-x,Nbx)2O7 (STN, x = 0.3) is suitable for use as ferroelectric materials for ferroelectric memory field-effect transistors (FETs), because it has a low dielectric constant and a high heat resistance. A new technology that enables the control of the orientation and properties (with a low dielectric constant and a large coercive field) of the STN film formed on an IrO2 film has been developed. We have successfully fabricated perovskite STN films with (110) and (172) orientations by controlling the crystal orientation of IrO2. An metal-ferroelectric-metal-insulator-Si (MFMIS) structure device with a large memory window of 2.5 V under 5 V writing operation has successfully been fabricated. Furthermore, the operation of the MFMIS FET, whose floating gate is IrO2 only, has been achieved for the first time.
- Controlling crystal orientation of ferroelectric
- Large memory window
- MFMIS-FET with IrO floating gate
- Sr(Ta,Nb)O (STN)