A method for the selective formation of epitaxial layers is described herein. In the method, epitaxial layers are deposited to form source and drain regions around a horizontal gate all around (hGAA structure). The method includes co-flowing a combination of chlorinated silicon containing precursors, antimony containing precursors, and n-type dopant precursors. The resulting source and drain regions are selectively grown from crystalline nanosheets or nanowires of the hGAA structure over the non-crystalline gate structure and dielectric layers. The source and drain regions are predominantly grown in a direction.