Electrical biosensors have attracted increasing attention in such fields as point-of-care testing, drug discovery, and healthcare products. In order for next-generation biosensor platforms to become more useful in our daily lives, it will be necessary to significantly improve their sensitivity, specificity, and parallelism. A precisely designed thin layer in molecular dimension on a solid substrate is essential for biosensing. The surfaces of biosensors are designed to capture target bioanalytes. In addition, the solid/liquid interface plays an important role in realizing additional functionalities such as target manipulation, signal stabilization, and switching. A functional interface combined with a field-effect device would enable on-demand label-free biosensing in a portable format. In this chapter, we provide an overview of biomolecular recognition in the context of electrochemical sensing and biosensing. Also, we review recent progress and trends in biosensing, including our own research.