A MEMS device includes a fixed structure and suspended structure including an internal structure and a first arm and a second arm. Each arm has a first end fixed to the fixed structure and a second end fixed to the internal structure. The ends are angularly arranged at a distance apart. Piezoelectric actuators mounted to the arms are driven so as to cause deformation of the arm and produce a rotation of the internal structure. In a resting condition, each of the first and second arms has a respective elongated portion with a respective concavity. The internal structure extends in part within the concavities of the elongated portions of the first and second arms.