High epsilon Gate Dielectrics Gd sub 2 O sub 3 and Y sub 2 O sub 3 for Si

New dielectric materials of Gd sub 2 O sub 3 (epsilon = 12) and Y sub 2 O sub 3 (epsilon = 18) were prepared in both single crystal and amorphous forms as gate oxide for Si by ultrhigh vacuum vapor deposition. The use of vicinal Si (100) substrates is shown to be the key to epitaxial growth of (110) oriented, single-domain films in the Mn sub 2 O sub 3 structure. Typical leakage current results are 10 sup (-5) A/cm sup 2 at 1V for an epitaxial Gd sub 2 O sub 3 film 34angstroms thick at an equivalent SiO sub 2 thickness of 19angstroms. A very low leakage of 10 sup (-6) A/cm sup 2 at 1V, and s specific capacitance as high as 35 fF/mu sup 2 were demonstrated for an amorphous Y sub 2 O sub 3 dielectric film 45angstroms thick at an equivalent SiO sub 2 thickness of 10angstroms. The C-V curves of both epitaxial and amorphous films showed the transition from accumulation to depletion, inversion of carriers, and little hysteresis in reverse sweeping. For all the Gd sub 2 O sub 3 films, the absence of SiO sub 2 at the interface is established from infrared absorption measurements.