A semiconductor manufacturing process for wafer-to-wafer stacking of a reconstituted wafer with a second wafer creates a stacked (3D) IC. The reconstituted wafer includes dies, die interconnects and mold compound. When stacked, the die interconnects of the reconstituted wafer correspond to die interconnects on the second wafer. Wafer-to-wafer stacking improves throughput of the manufacturing process. The reconstituted wafer may include dies of different sizes than those in the second wafer. Also, the dies of the reconstituted wafer may be singulated from a wafer having a different size than the second wafer. Thus, this wafer-to-wafer manufacturing process may combine dies and/or wafers of dissimilar sizes.