Semiconductor devices and methods of manufacturing the semiconductor devices are described herein. A method includes forming an interconnect structure over a device wafer. The device wafer includes a first integrated circuit, a semiconductor substrate, and a redistribution structure. The method further includes forming a metallization layer and a group of dummy insertion structures having a stepped pattern density in a topmost dielectric layer of the interconnect structure. The group of dummy insertion structures and the metallization layer are planarized with the dielectric layer. The method further includes forming a first bonding layer over the group of dummy insertion structures, the metallization layer, and the dielectric layer. The method further includes bonding a carrier wafer to the first bonding layer, forming an opening through the semiconductor substrate, and forming a conductive via in the opening and electrically coupled to the redistribution structure.