Capacitive pressure sensor and preparation method

The invention discloses a capacitive pressure sensor, including a SOI (Silicon-On-Insulator) silicon chip, a single crystalline silicon layer, a silicon dioxide layer and polysilicon layers. The SOI silicon chip is internally provided with a vacuum seal cavity. The silicon dioxide layer comprises with a first supporting layer, a second supporting layer and a third supporting layer which are identical in height and arranged in parallel. The first supporting layer is located in an upper area in the vacuum seal cavity. The second supporting layer and the third supporting layer are located outside of the upper area in the vacuum seal cavity. The second supporting layer is positioned between the first supporting layer and the third supporting layer. The polysilicon layers comprise a first polysilicon layer and a second polysilicon layer. The first polysilicon layer is fixedly connected on the first supporting layer and the second supporting layer. The second polysilicon layer is fixedly connected on the third supporting layer. One end surface of the first polysilicon layer is opposite to one end surface of the second polysilicon layer. The sensor has high efficiency and sensitivity in performance analysis. Meanwhile, the invention provides a preparation method of the sensor, and the preparation method is simple and easy to implement.