A MEMS device having a body with a first and a second surface, a first portion and a second portion. The MEMS device further has a cavity extending in the body from the second surface; a deformable portion between the first surface and the cavity; and a piezoelectric actuator arranged on the first surface, on the deformable portion. The deformable portion has a first region with a first thickness and a second region with a second thickness greater than the first thickness. The second region is adjacent to the first region and to the first portion of the body.