Physical Unclonable Function (PUF) has recently attracted interest from both industry and academia as a potential alternative approach to secure Internet of Things (IoT) devices from the more traditional computational-based approach using conventional cryptography. PUF is a promising solution for lightweight security, where the manufacturing fluctuation process of IC is used to improve the security of IoT as it provides low complexity design and preserves secrecy. PUF provides a low-cost low-power solution and can be implemented in both Field Programmable Gate Arrays (FPGA) and Application-Specific Integrated Circuits (ASICs). In this survey, we provide a comprehensive review of the state-of-the-art of PUF, its architectures, protocols and security for IoT.