The possibility of fabricating a full graphene device was investigated by utilizing atomic layer etching (ALET) technology. By using O₂ ALET which functions by oxygen radical adsorption followed by the removal of the oxygen chemisorbed on carbon, the removal of exactly one graphene layer per ALET cycle was detected through the increase of the transmittance by 2.3% after one ALET cycle and by the decrease of the G peak in the Raman spectra. The Raman spectra also showed an increase of the D peak after ALET, indicating the formation of physical damage on the graphene surface layer. This damage was mostly recovered by hydrogen annealing at 1000°C after ALET. Full graphene field effect transistors (source, drain: 3 layer, channel: 1, 2, 3 layer) were fabricated by reducing the channel layers using ALET, followed by annealing, and the electrical characteristics of the devices showed the possibility of fabricating fully functional graphene devices composed of an all graphene source/drain and graphene channel by utilizing ALET.