A semiconductor device includes a memory cell including a write transistor and a read transistor that are electrically connected to each other. The write transistor includes a write bit line disposed over a substrate, a write channel structure disposed on the write bit line and extending in a direction perpendicular to a surface of the substrate on the write bit line, a write gate dielectric layer disposed on a side surface of the write channel structure, and a write word line disposed on the write gate dielectric layer. The read transistor includes a read gate electrode layer disposed on the write channel structure, a read gate dielectric layer disposed on the read gate electrode layer, a read channel layer disposed on the read gate dielectric layer, and a read word line and a read bit line that are disposed at opposite ends of the read channel layer.