A MEMS device is formed in a die of semiconductor material having a cavity defined therein and having an anchorage portion. A tiltable structure is elastically suspended over the cavity and has a main extension in a horizontal plane. First and second supporting arms extend between the anchorage portion and opposite sides of the tiltable structure. First and second resonant piezoelectric actuation structures are intended to be biased to thereby cause rotation of the tiltable structure about a rotation axis. The first supporting arm is formed by first and second torsion springs, which are rigid to movements out of the horizontal plane and compliant to torsion about the rotation axis and are coupled together at a constraint region. The first and second resonant piezoelectric actuation structures extend between the anchorage portion and the constraint structure, on first and second sides of the first supporting arm.