The discovery of ferroelectricity in hafnium oxide (HfO₂) thin films renewed the interest in ferroelectric nonvolatile memories. In particular, not only ferroelectric capacitors but also ferroelectric field-effect transistor based on this material have now become appealing concepts. This is mainly due to robust ferroelectric properties even upon aggressive scaling and to the compatibility with common fabrication processes used in the semiconductor industry. In this chapter, we review the key achievements of HfO₂-based FeFETs since their first report in 2012. First, material properties of HfO₂ for memory applications are briefly summarized, discussing the impact of doping as well as the electrical switching and reliability characteristics. Then, FeFETs having a 10-nm-thick silicon-doped HfO₂ layer in the gate stack are illustrated, and their main figures of merit are discussed, including memory window, write and read operations, endurance and retention aspects as well as parasitic charge trapping. Finally, the integration in advanced technology nodes and the performance of large active memory arrays is shown.