A transistor includes a gate electrode, a ferroelectric layer, a channel layer, a gas impermeable layer, a dielectric layer, a source line and a bit line. The ferroelectric layer is disposed on the gate electrode. The channel layer is disposed on the ferroelectric layer. The gas impermeable layer is disposed in between the channel layer and the gate electrode, and in contact with the ferroelectric layer. The dielectric layer is surrounding the ferroelectric layer and the channel layer, and in contact with the gas impermeable layer. The source line and the bit line are embedded in the dielectric layer and connected to the channel layer.