Because of the nature of their one-dimensional structure, good conductivity and excellent ballistic transport property, single-walled carbon nanotubes have been considered as an important nanomaterial in building a new generation of electrical circuits. In this article, we mainly focus on two strategies developed for installing diverse functionalities into single-walled carbon nanotube-based molecular transistors: nanolithographic method and surface chemical modification. To overcome ill-defined contacts between molecules and electrodes, we highlight the current effort and direction in the creation of reliable single-molecule devices using carboxylic acid-functionalized single-walled carbon nanotubes as nanogapped point contacts. These contacts are made by high-resolution electron beam lithography and oxygen plasma oxidative etching. Electrically functional molecules are then covalently bridged into the nanogaps through robust amide linkages, thus forming stable molecular electronic devices. These results open up new opportunities to develop unique single-molecule biosensors with high selectivity and high speed, which hold great promise in both industrial applications and basic scientific researches.