A manufacturing method of a semiconductor device is provided in an embodiment of the present invention. The manufacturing method includes the following steps. A transistor is formed on a substrate. The transistor includes a plurality of semiconductor sheets and two source/drain structures. The semiconductor sheets are stacked in a vertical direction and separated from one another. Each of the semiconductor sheets includes two first doped layers and a second doped layer disposed between the two first doped layers in the vertical direction. A conductivity type of the second doped layer is complementary to a conductivity type of each of the two first doped layers. The two source/drain structures are disposed at two opposite sides of each of the semiconductor sheets in a horizontal direction respectively, and the two source/drain structures are connected with the semiconductor sheets.