Methods of forming field effect transistors (FETs) having fin-shaped active regions include patterning a semiconductor substrate to define a fin-shaped semiconductor active region therein, which is surrounded by a trench. At least an upper portion of the fin-shaped semiconductor active region is covered with a sacrificial layer. This sacrificial layer is selectively etched-back to define sacrificial spacers on sidewalls of the fin-shaped semiconductor active region. The electrically insulating region is formed on the sacrificial spacers. The sacrificial spacers are then removed by selectively etching the sacrificial spacers using the electrically insulating region as an etching mask. An insulated gate electrode is then formed on the sidewalls of the fin-shaped semiconductor active region.