A microelectromechanical mirror device (1; 100), comprising a die of semiconductor material having: a fixed structure defining a cavity ; a tiltable structure carrying a reflecting region , elastically suspended above the cavity and having a main extension in a horizontal plane (xy); at least one first pair of driving arms , coupled to the tiltable structure and carrying respective piezoelectric material regions , configured to be biased to cause a rotation of the tiltable structure around a rotation axis (X) parallel to a first horizontal axis (x) of said horizontal plane; elastic suspension elements , configured to elastically couple said tiltable structure to said fixed structure at said rotation axis (X), being stiff with respect to movements out of the horizontal plane (xy) and yielding with respect to torsion around said rotation axis (X); and a piezoresistive sensor , configured to provide a detection signal (S r ) indicative of the rotation of the tiltable structure around the rotation axis (X), characterized by comprising at least one test structure , integrated in said die and configured to provide a calibration signal (S c ) indicative of a sensitivity variation of the piezoresistive sensor , configured to be used for calibration of said detection signal (S r ), wherein the sensitivity variation of the piezoresistive sensor is due to geometry variations; and wherein said test structure comprises piezoelectric actuators (38,39; 44) and a movable mass (32; 40) configured to be operated in resonance by actuation of the piezoelectric actuators (38,39; 44), the resonance frequency associated with said test structure (30; 30') having a variation which is a function of said geometry variations and correlated to a variation of said sensitivity of the piezoresistive sensor ; wherein said calibration signal (S c ) is indicative of the variation of said resonance frequency. a fixed structure defining a cavity ; a tiltable structure carrying a reflecting region , elastically suspended above the cavity and having a main extension in a horizontal plane (xy); at least one first pair of driving arms , coupled to the tiltable structure and carrying respective piezoelectric material regions , configured to be biased to cause a rotation of the tiltable structure around a rotation axis (X) parallel to a first horizontal axis (x) of said horizontal plane; elastic suspension elements , configured to elastically couple said tiltable structure to said fixed structure at said rotation axis (X), being stiff with respect to movements out of the horizontal plane (xy) and yielding with respect to torsion around said rotation axis (X); and a piezoresistive sensor , configured to provide a detection signal (S r ) indicative of the rotation of the tiltable structure around the rotation axis (X), characterized by comprising at least one test structure , integrated in said die and configured to provide a calibration signal (S c ) indicative of a sensitivity variation of the piezoresistive sensor , configured to be used for calibration of said detection signal (S r ), wherein the sensitivity variation of the piezoresistive sensor is due to geometry variations; and wherein said test structure comprises piezoelectric actuators (38,39; 44) and a movable mass (32; 40) configured to be operated in resonance by actuation of the piezoelectric actuators (38,39; 44), the resonance frequency associated with said test structure (30; 30') having a variation which is a function of said geometry variations and correlated to a variation of said sensitivity of the piezoresistive sensor ; wherein said calibration signal (S c ) is indicative of the variation of said resonance frequency. <EOS>