The present application discloses a semiconductor device and a method for fabricating the semiconductor device. The semiconductor device includes a first stack structure positioned on a first substrate, a first impurity region and a second impurity region respectively positioned on opposing sides of the first stack structure and operatively associated with the first stack structure, a second stack structure positioned above the first stack structure with a middle insulation layer interposed therebetween, and a third impurity region positioned on one side of the second stack structure and electrically coupled to the second impurity region. The first stack structure includes a plurality of first semiconductor layers and a plurality of gate assemblies alternatively arranged. The plurality of gate assemblies includes a gate dielectric and a gate electrode. The second stack structure includes a plurality of second semiconductor layers and a plurality of capacitor sub-units alternatively arranged. The plurality of capacitor sub-units including a capacitor dielectric and a capacitor electrode.