A two-dimensional semiconductor is configured for contacting two metals and includes a first semiconductor layer and a plurality of second semiconductor layers. The first semiconductor layer includes a channel region and two metal contacting regions. The two metal contacting regions are connected to two sides of the channel region, respectively. A plurality of heterojunctions having type-II band alignment are formed by the second semiconductor layers and the two metal contacting regions of the first semiconductor layer, respectively, and the heterojunctions are arranged and spaced away from each other. |