Abstract: A transistor includes an insulating layer, a source region, a drain region, a channel layer, a ferroelectric layer, and a gate electrode. The source region and the drain region are respectively disposed on and in physical contact with two opposite sidewalls of the insulating layer. A thickness of the source region, a thickness of the drain region, and a thickness of the insulating layer are substantially the same. The channel layer is disposed on the insulating layer, the source region, and the drain region. The ferroelectric layer is disposed over the channel layer. The gate electrode is disposed on the ferroelectric layer.