Method of forming material layer

A method of forming a material film, the method comprising:

• providing a non-photosensitive mask on a substrate, the non-photosensitive mask exposing a partial region of the substrate;
• forming a material film on the partial region of the substrate using a sputtering process;
• removing the non-photosensitive mask from the substrate;
• and
• heat-treating the substrate and the material film from which the non-photosensitive mask is removed under a first gas atmosphere, wherein
• the material film includes a transition metal and a chalcogen element,
• the material film is represented by MX(2-a)Ya(0≤a<2) after the forming the material film on the partial region of the substrate using the sputtering process is performed and before the heat-treating the substrate and the material film is performed, and
• in the MX(2-a)Ya(0≤a<2),
• M is at least one of Ti, Zr, Hf, Ta, Mo, W, Tc, Re, Co, Rh, Ir, Ni, Pd, Pt, Zn, or Sn,
• X is S, Se, or Te, and
• Y is Nb, V, or Ti.