“…The large polarization of ferroelectrics enables various materials as the channel, including Si, [4][5][6] Ge, 7) GaAs, 8) La 1.99 Sr 0.01 CuO 4 , 9) SrRuO 3 , 10) indium tin oxide, 11,12) indium gallium zinc oxide, 13) ZnO, [14][15][16] VO 2 , 17) and GaN. 18) After Böscke et al 19) and J. Müller et al 20) demonstrated ferroelectricity in Si-doped HfO 2 and Zr 0.5 Hf 0.5 O 2 ultrathin films, ferroelectric HfO 2 and its application to FGTs with a HfO 2 -based ferroelectric gate and a bulk Si channel have been intensively studied because of the compatibility with Si-CMOS technology and its scalability to technology nodes below 45 nm. 2,3,21,22) For example, in 2013, nonvolatile memory operation of an FGT with a 10 nm-thick HfO 2 layer fabricated using 28 nm technology was reported.…”