US Patent 9721927 Semiconductor device, structure and methods

A 3D semiconductor device, including: a first die including first transistors and first interconnect, overlaid by a second die including second transistors and second interconnect, where the first die has a first die area and the second die has a second die area, where the first die area is at least 10% larger than the second die area, and where the second die has a thickness of less than four microns.