As the technology has grabbed a lot attention, the Micro-Electro-Mechanical Systems (MEMS)-based capacitive pressure sensors are the promising devices with good performance. These are capable of observing the temporal effects of the environment and to calibrate the values in order to provide information regarding the physical parameters by studying the deflection of the diaphragm structure. This paper presents a new model of capacitive pressure sensor along with a complementary metal–oxide–semiconductor (CMOS). The stress–strain characterization of poly-SiGe is used to develop and model the structure of the sensor’s diaphragm element. The alternate edge supported octagonal-structured diaphragm held pentagonal-shaped clamps to yield good linearity, wide dynamic range, and better sensitivity. To improve the central deflection of the octagonal diaphragm, alternate opposite edges are fixed to divert the entire stress to the center of the diaphragm. The circuit presented over here uses a sigma–delta technique to convert the input capacitance into digital form. A constant-g m biasing technique is used for high-temperature performance. The entire structure of the sensor is modeled in COMSOL Multiphysics, and the interface electronics are designed in Mentor Graphics using UMC 90 nm technology and achieves a better gain of 57-dB at the readout of the circuit. Simulation results show better sensitivity of 0.028 fF/hPa (for 1.8 V supply), and the nonlinearity is around 1% for the full scale applied pressure range from 0 Pa to 1500 hPa, the sensor is interfaced with the CMOS circuitry. The intelligent sensor is around 500 µm × 500 µm with the side of the octagonal diaphragm being 146.443 µm, respectively. Compared to commercial pressure sensor this device achieves wider low-pressure sensing range at minimum supply voltage. © 2018, Springer Nature Singapore Pte Ltd.