An optical device including a two-dimensional material and a method of manufacturing the same are provided. The optical device may include a barrier stack formed on a bottom channel layer, a top channel layer formed on the barrier stack, a drain electrode connected to the bottom channel layer, a source electrode formed on a substrate. The barrier stack may include two or more barrier layers, and one or more channel units at least partially interposing between the barrier layers. Channel units connected to the drain electrode and channel units connected to the source electrode may be formed, in an alternating sequence, between barrier layers included in the barrier stack. The barrier layers may each have a thickness which is less than a distance which may be traveled by electrons and holes generated by photo absorption prior to recombination. As a result, the optical device may provide improved photo separation efficiency.