A MEMS device includes a fixed structure and a mobile structure with a reflecting element coupled to the fixed structure through at least a first deformable structure and a second deformable structure. Each of the first and second deformable structures includes a respective number of main piezoelectric elements, with the main piezoelectric elements of the first and second deformable structures configured to be electrically controlled for causing oscillations of the mobile structure about a first axis and a second axis, respectively. The first deformable structure further includes a respective number of secondary piezoelectric elements configured to be controlled so as to vary a first resonance frequency of the mobile structure about the first axis.