Abstract: A method of fabricating a power semiconductor device includes forming a bi layer mask on a semiconductor substrate, where the bilayer mask comprises a first dielectric layer on the semiconductor substrate and a second dielectric layer on the first dielectric layer. The first and second dielectric layers are through-etched to define an exposed portion of the semiconductor substrate. The first dielectric layer is selectively etched to form an undercut region of the bi layer mask. A crystalline semiconductor material is epitaxially grown on the exposed portion of the semiconductor substrate, and a polycrystalline semiconductor material is deposited on the second dielectric layer of the bilayer mask. After the epitaxial growth, the bilayer mask and the polycrystalline semiconductor material are removed from the semiconductor substrate, leaving behind a mesa comprising the crystalline semiconductor material on the semiconductor substrate.