A method for fabricating a semiconductor device includes forming a plurality of first trenches by etching a substrate, forming first spacers covering both sidewalls of each of the first trenches, forming a plurality of second trenches by etching a bottom of each of the first trenches, forming second spacers covering both sidewalls of each of the second trenches, forming a plurality of third trenches by etching a bottom of each of the second trenches, forming an insulation layer covering exposed surfaces of the plurality of the substrate, and forming a contact which exposes one sidewall of each of the second trenches by selectively removing the second spacers.