Abstract: For the metal-oxide-semiconductor（MOS） structure, the change of the back-gate voltage causes the change of the surface potential in the silicon, which leads to the change of the conductance. This principle has been fully studied and applied in field effect transistors, and its application in the field of planar electron tubes is discussed for the first time in this paper. By measuring the current flowing through the silicon, the influence of gate voltage on the silicon surface potential with different thickness and carrier concentration is analyzed, and the phenomenon of electron accumulation and depletion in the silicon is verified. The experimental results show that for devices with different silicon carrier concentration and thickness, the same gate voltage changes will cause different conductance changes. The change of emission current caused by the gate also proves the ability of the gate to regulate the silicon surface potential. In the case of a planar nanoscale vacuum/air channel tube（PNVCT）, electrons escape from the cathode surface and are captured by the anode to form the emission current. Therefore, the change of the silicon surface potential can cause the change of the number of electrons emitted, which causes the change of the emission current, and makes it possible to realize the PNVCT in which the silicon works as the cathode and the emission current can controlled by the back-gate voltage.