Method of forming amorphous layer of boron nitride and method of forming amorphous material layer

A method of forming an amorphous material layer, the method comprising:

• placing a target substrate having a deposition surface in a reaction chamber;
• depositing a thin film of a target material on the deposition surface by exposing the deposition surface to a precursor of the target material;
• plasma-treating the thin film of the target material;
• maintaining the thin film of the target material at a process pressure lower than a process pressure during the plasma-treating for a certain maintaining time after the plasma-treating;
• and
• repeating multiple times the depositing of the thin film of the target material, the plasma-treating of the thin film of the target material, and the maintaining of the thin film of the target material.