A design of barometric pressure sensor is presented in this paper, which is compatible with the standard complementary metal-oxide semiconductor process, and can solve the problem of the electrode feed-through out of the sealed cavity at the same time. Both electrodes of the sensor are led from the top side of the chip. Mechanical characteristics of the sensor are theoretically analyzed based on the plate theory and evaluated by finite element analysis. Square membrane sensors with side lengths of 300, 500, and 700 μm were fabricated, providing a measured sensitivity of 0.9. 1.2, and 1.7 fF/hPa, respectively. The nonlinearity of the sensor is less than 3.1% over a dynamic range 500 to 700 hPa. The experimental results and the theoretical analysis show that the device is suitable to be used in measuring the low pressure, and is more sensitive when the initial gap of the capacitor is smaller.