A semiconductor device includes a substrate, at least one first semiconductor layer, and at least one second semiconductor layer. The at least one first semiconductor layer is disposed on the substrate, and the at least one second semiconductor layer is disposed on the at least one first semiconductor layer. The at least one first semiconductor layer includes a first doping portion, a second doping portion, a channel, and a semiconductor film. The second doping portion is adjacent to the first doping portion. The channel is disposed between the first doping portion and the second doping portion, and disposed with the substrate in parallel. The semiconductor film is disposed around the channel.