Abstract: The piezoresistive pressure sensor (1) comprises a rigid flat support (2), a flat flexible membrane (3) having a flat external face (4) exposed to a pressure of a fluid and a flat internal face (5) delimiting in cooperation with a flat internal face (7) of the support (2) a chamber (9) accommodating the deformation of the membrane (3), an electrical measuring circuit comprising a resistive Wheatstone bridge (10) applied on the flat internal face (5) of the membrane (3) for detecting the deformation of the membrane (3), and at least an electrical resistor (Rc) for calibrating the value of the output signal when the fluid is at a reference pressure, the calibration resistor (Rc) being applied on the flat internal face (5) of the membrane (3).