A semiconductor device comprising: a two-dimensional material layer including a two-dimensional semiconductor material having a polycrystalline structure; metallic nanoparticles partially on the two-dimensional material layer, wherein the metallic nanoparticles are on at least one of a defect of the two-dimensional semiconductor material and a grain boundary of the two-dimensional semiconductor material; a source electrode and a drain electrode respectively on both sides of the two-dimensional material layer; and a gate insulating layer and a gate electrode on the two-dimensional material layer between the source electrode and the drain electrode, wherein the two-dimensional material layer comprises a first region and a second region, the gate electrode is on the first region of the two-dimensional material layer, and the source electrode and the drain electrode are on the second region of the two-dimensional material layer, and characterized in that at least one of: the metallic nanoparticles are on the second region of the two-dimensional material layer at a higher density than a density of the metallic nanoparticles on the first region of the two-dimensional material layer; and the metallic nanoparticles comprise first metallic nanoparticles and second metallic nanoparticles, the first metallic nanoparticles are on the first region of the two-dimensional material layer, the second metallic nanoparticles are on the second region of the two-dimensional material layer, and a material of the second metallic nanoparticles is different from a material of the first metallic nanoparticles. a two-dimensional material layer including a two-dimensional semiconductor material having a polycrystalline structure; metallic nanoparticles partially on the two-dimensional material layer, wherein the metallic nanoparticles are on at least one of a defect of the two-dimensional semiconductor material and a grain boundary of the two-dimensional semiconductor material; a source electrode and a drain electrode respectively on both sides of the two-dimensional material layer; and a gate insulating layer and a gate electrode on the two-dimensional material layer between the source electrode and the drain electrode, wherein the two-dimensional material layer comprises a first region and a second region, the gate electrode is on the first region of the two-dimensional material layer, and the source electrode and the drain electrode are on the second region of the two-dimensional material layer, and characterized in that at least one of: the metallic nanoparticles are on the second region of the two-dimensional material layer at a higher density than a density of the metallic nanoparticles on the first region of the two-dimensional material layer; and the metallic nanoparticles comprise first metallic nanoparticles and second metallic nanoparticles, the first metallic nanoparticles are on the first region of the two-dimensional material layer, the second metallic nanoparticles are on the second region of the two-dimensional material layer, and a material of the second metallic nanoparticles is different from a material of the first metallic nanoparticles. the metallic nanoparticles are on the second region of the two-dimensional material layer at a higher density than a density of the metallic nanoparticles on the first region of the two-dimensional material layer; and the metallic nanoparticles comprise first metallic nanoparticles and second metallic nanoparticles, the first metallic nanoparticles are on the first region of the two-dimensional material layer, the second metallic nanoparticles are on the second region of the two-dimensional material layer, and a material of the second metallic nanoparticles is different from a material of the first metallic nanoparticles.