To illustrate an application of the field effect transistor (FET) structure, this study suggests a new cantilever, using atomic force microscopy (AFM), for sensing surface potentials in nanoscale. A combination of the microelectromechanical system technique for surface and bulk and the complementary metal oxide semiconductor process has been employed to fabricate the cantilever with a silicon-on-insulator (SOl) wafer. After the implantation of a high-ion dose, thermal annealing was used to control the channel length between the source and the drain. The basic principle of this cantilever is similar to the FET without a gate electrode.