The ferroelectric behavior of capacitors based on hafnium oxide dielectrics is reported. Thin films of 7-30 nm thickness were found to exhibit ferroelectric polarization-voltage hysteresis loops when integrated into TiN-based metal-insulator-metal capacitors. A remanent polarization up to 25 μC/cm² and a coercive field of about 1 MV/cm was observed when Si:HfO₂ was used as a ferroelectric material. Switching times of 10 ns were demonstrated and the ferroelectric properties were verified in the temperature range from 80 K to 470 K. N-channel MFIS-FETs (Metal-Ferroelectric- Insulator-Semiconductor Field-Effect Transistors) with poly-Si/TiN/Si:HfO ₂/SiO₂/Si gate stack with a gate length equal or below 260 nm were successfully fabricated. The switching characteristics, endurance and retention properties were analyzed. A memory window of 1.2 V was obtained. Endurance performance of up to 10⁴ cycles was verified. Retention characteristics were measured and 10 years data retention was extrapolated at 25 °C and 150 °C.