A liquid crystal display device and a fabricating method thereof for simplifying a process and improving an aperture ratio are disclosed, including forming a first mask pattern group including a gate line, a gate electrode and a common line; forming a second mask pattern group including a semiconductor pattern and a source/drain pattern having a data line, a source electrode and a drain electrode overlapped thereon on the gate insulating film using a second mask; and forming a third mask pattern group including and a pixel electrode making an interface with the protective film in the pixel hole to be connected to the drain electrode, thereby forming a horizontal electric field with the common electrode, using a third mask.