methods of forming an electronic device may include forming a gate electrode on a semiconductor substrate , and forming first and second impurity doped regions of the semiconductor substrate on opposite sides of the gate electrode . an insulating layer may be formed on the semiconductor substrate including the first and second impurity doped regions , and first and second holes may be formed in the insulating layer , with the first and second holes respectively exposing portions of the first and second impurity doped regions . in addition , first and second epitaxial semiconductor layers may be formed in the respective first and second holes on the exposed portions of the first and second impurity doped regions of the semiconductor substrate . related devices are also discussed .