MOS varactors with ferroelectric films

The microwave performance of MOS varactors with additional ferroelectric film (MFOS) is presented. The tunability of MFOS varactors above 20 GHz is more than 10% higher than that of simple MOS varactors, with sufficiently high Q factor. The proposed MFOS varactor has a simple design and is compatible with standard CMOS processes. It may have symmetric C-V curves at rather high tuning voltages and superior performance at millimetre wave frequencies. In experiments varactors are based on NaNbO/sub 3/ films grown on high resistivity silicon substrates.