Methods of fabricating a lanthanum oxide layer, and methods of fabricating a MOSFET and/or a capacitor especially adapted for semiconductor applications using such a lanthanum oxide layer are disclosed. The methods include a preliminary step of disposing a semiconductor substrate into a chamber. Tris(bis(trimethylsilyl)amino)Lanthanum as a lanthanum precursor is then injected into the chamber such that the lanthanum precursor is chemisorbed on the semiconductor substrate. Then, after carrying out a first purge of the chamber, at least one oxidizer is injected into the chamber such that the oxidizer is chemisorbed with the lanthanum precursor on the semiconductor substrate. Then, the chamber is purged a second time. The described steps of injecting the lanthanum precursor into the chamber, first-purging the chamber, injecting an oxidizer into the chamber, and second-purging the chamber may be sequentially and repeatedly performed to form a lanthanum oxide layer of a desired thickness having enhanced semiconductor characteristics.