We propose a novel fabrication process for twin probes of an atomic force microscope (AFM) that consist of a silicon dual tip with a narrow gap. The dual tip with a tetrahedral shape consists of an inclined silicon (111) plane and two vertical planes and was successfully fabricated by using the proposed fabrication process of combining deep reactive ion etching (D-RIE) for silicon trench formation along the silicon (001) direction, selective oxidation of the sidewalls of the trench, and crystalline anisotropic etching. The silicon tips could be sharpened by a low-temperature oxidation process, resulting in a tip radius of about . In addition, the dual silicon tip formation, dual AFM probe with cantilever, and thermal actuator were also successfully fabricated from a silicon-on-insulator (SOI) water. The gap of the dual tip was about , with trench etching wide and sidewall oxidation thick.