US Patent 11837643 Method for manufacturing memory device

A semiconductor device includes a substrate, a gate structure disposed over the substrate, a drain structure disposed in the substrate, and a source structure disposed in the substrate on an n opposite side of the gate structure from the drain structure. The substrate includes a first semiconductor layer, a second semiconductor layer over the first semiconductor layer, and an insulating layer sandwiched between the first semiconductor layer and the second semiconductor layer. The source structure and the drain structure include a same conductivity type. The source structure includes at least an epitaxial layer. The source structure extends deeper into the substrate than the drain structure.