A 1024-bit, 1/2 -rate fully parallel low density parity check (LDPC) code decoder has been designed and implemented using a 3D 0.18/spl mu/m fully depleted silicon-on-insulator (FDSOI) CMOS technology based on wafer bonding. The taped-out 3D decoder with about 8M transistors was simulated to have a high throughput of 2Gb/s and a low power consumption of only 430mW using 6.4/spl mu/m by 6.3/spl mu/m of die area. The 3D implementation is estimated to offer more than 10/spl times/ power-delay-area product improvement over its corresponding 2D implementation. This first large-scale 3D ASIC with fine-grain (5/spl mu/m) vertical interconnects is made possible by jointly developing a complete automated 3D design flow from a commercial 2D design flow combined with the needed 3D-design point tools.