A graphene device may include a channel layer including graphene, a first electrode and second electrode on a first region and second region of the channel layer, respectively, and a capping layer covering the channel layer and the first and second electrodes. A region of the channel layer between the first and second electrodes is exposed by an opening in the capping layer. A gate insulating layer may be on the capping layer to cover the region of the channel layer, and a gate may be on the gate insulating layer.