We describe a substrate for a Legged Chip, a CMOS integrated circuit with built in actuation mechanisms for motion. We have designed and fabricated a custom integrated circuit using a commercial 0.5μm CMOS technology which implements walking gait control. The circuit specifications and physical implementation have been designed to take into consideration the addition of thermal actuators through low- temperature MEMS surface processing on fabricated CMOS dies. External connections will be limited to two leads for providing power and ground. This work represents progress towards a fully autonomous mobile integrated circuit.