In this paper, an ultra-small MEMS-based flexible capacitive sensor is proposed. Finite element analysis (FEA) simulation tool is used to design and analyze the sensor performance for a uniaxial uniform pressure range of 0-50 kPa applied to sensor geometry’s top surface. The sensor characteristics such as a change in sensor capacitance, total surface displacement with external pressure effect, capacitance relative change with pressure are analyzed with the finite element method. The sensor’s obtained result for flat-panel dielectric structure exhibits a linear response for a pressure range of 0-50 kPa and sensitivity of $0.63 \times 10^{-3}$ fF/ [kPa]. However, to improve the sensitivity of sensor micro cuboid and truncated pyramid structured dielectric layer is introduced, which results in effectively enhanced sensor characteristics. The sensor shows a linear response with improved sensitivity of $16.8 \times 10^{-3}$ fF/ [kPa] for cuboid and $19.4 \times 10^{-3}$ fF/ [kPa] for truncated pyramid dielectric structure. The simulation-based analysis indicates that the microstructured dielectric can enhance large deformation and effectively improve the device’s sensitivity.