A semiconductor device assembly that includes first and second semiconductor devices connected directly to a first side of a substrate and a plurality of interconnects connected to a second side of the substrate. The substrate is configured to enable the first and second semiconductor devices to communicate with each other through the substrate. The substrate may be a silicon substrate that includes complementary metal-oxide-semiconductor (CMOS) circuits. The first semiconductor device may be a processing unit and the second semiconductor device may be a memory device, which may be a high bandwidth memory device. A method of making a semiconductor device assembly includes applying CMOS processing to a silicon substrate, forming back end of line (BEOL) layers on a first side of the substrate, attaching a memory device and a processing unit directly to the BEOL layers, and forming a redistribution layer on the second side of the substrate.