Embodiments of the invention include a partially insulated field effect transistor and a method of fabricating the same. According to some embodiments, a semiconductor substrate is formed by sequentially stacking a bottom semiconductor layer, a sacrificial layer, and a top semiconductor layer. The sacrificial layer may be removed to form a buried gap region between the bottom semiconductor layer and the top semiconductor layer. Then, a transistor may be formed on the semiconductor substrate. The sacrificial layer may be a crystalline semiconductor formed by an epitaxial growth technology.