Semiconductor structures and processes for fabricating semiconductor structures comprising hafnium oxide layers modified with lanthanum oxide or a lanthanide-series metal oxide are provided. A semiconductor structure in accordance with an embodiment of the invention comprises an amorphous layer of hafnium oxide overlying a substrate. A lanthanum-containing dopant or a lanthanide-series metal-containing dopant is comprised within the amorphous layer of hafnium oxide. The process comprises growing an amorphous layer of hafnium oxide overlying a substrate. The amorphous layer of hafnium oxide is doped with a dopant having the chemical formulation LnO.sub.x, where Ln is lanthanum, a lanthanide-series metal, or a combination thereof, and X is any number greater than zero. The doping step may be performed during or after growth of the amorphous layer of hafnium oxide.