Method of separating substrate and method of fabricating semiconductor device using the same

A method of fabricating a semiconductor device, comprising:

• forming a first mask pattern comprising a masking region and an open region, on a substrate;
• forming a sacrificial layer covering the substrate and the first mask pattern;
• patterning the sacrificial layer to form a seed layer and to expose at least a portion of the first mask pattern;
• forming a second mask pattern on the exposed portion of the first mask pattern;
• forming an epitaxial layer on the seed layer and the second mask pattern, and forming a void between the second mask pattern and the epitaxial layer;
• forming a support substrate on the epitaxial layer;
• and
• separating the substrate from the epitaxial layer.