A ferroelectric field-effect transistor has been investigated using a thin film of bismuth titanate (Bi. TiJ0 12) deposited on a Si substrate by rf sputtering. Achievement of the ferroelectric polycrystalline Bi. TiJ0 12 films without any cracks necessitates post deposition heat treatment in air at temperatures ~ 550°C for 30 min.The film. heat treated at 650·C. has a remanent polarization of 4.0 p.C/cm2 and a coercive field of about 2S0 kV /cm at I kHz. A FET having a gate structure of Bi.Ti J 0 12 -Si0 2 -Si was fabricated. where the Si02 served to prevent charge injection from Si into the ferroelectric film. (This process would degrade the retention of memorized states.) The FET can be switched by voltages of as low as IS V applied to the gate. The on and off states are very stable at room temperature.

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A new n-channel MNOS technology for EAROM applications has been developed by introducing a threshold voltage control technique. The technology is principally based on a low energy implantation of boron ions for obtaining a positive center voltage in the threshold window, which results in better retentivity. By incorporating this MNOS technology and n-well CMOS technology on an isolated epitaxial layer, an n-channel MNOS EAROM is fabricated for TV electronic tuning system. The EAROM utilizes the two MNOS transistors per cell configuration. The device showed a long data retention time over 10 years at 80 °C after 105 erasing/writing cycles, therefore the technology appears to be quite promising for EAROM applications.