Metal gate and field board structure of radio frequency VDMOS transistor and manufacturing method thereof

The invention discloses a metal gate and field board structure of a radio frequency VDMOS transistor and a manufacturing method thereof. Wet etching is adopted to form a trapezoidal oxide layer in the middle of the surface of an epitaxial layer of a silicon substrate; a conventional process is adopted at two sides of the trapezoidal oxide layer to form conventional doping areas such as a channel and a source and a drain; a gate oxide layer then grows on the surface of the epitaxial layer and is coated by a metal layer, and wet etching is adopted to remove metal layers at side edges of the trapezoidal oxide layer; and dry etching is finally adopted to form the metal gate and field board structure. The metal gate can reduce gate resistance, the power gains of a device can be improved, separation between the gate and the field board can reduce gate-drain feedback capacitance, and the high-frequency performance of the device is improved; the distance between the gate and the field board can be adjusted through th