A capacitive level-sensor device comprises: —a circuit substrate made of electrically insulating material (20) that extends longitudinally according to a level-sensing axis; —a first array of electrodes or capacitive elements on a sensing region (23) of the circuit substrate (20), which comprises at least one first series of first electrodes (J1-Jn) coplanar to one another at a major face of the circuit substrate (20); —a circuit, which comprises circuit components associated to a second region (24) of the circuit substrate (20); and—a casing body (14-16), which comprises at least: a sensing portion (15), which is electrically insulating and fluid-tight and coats at least the sensing region (23) of the circuit substrate (20); and a mounting portion (14, 16), which coats at least partially the second region (24) of the circuit substrate (20) and is configured for fluid-tight fixing at an opening (6) of a container (1). The sensing portion (15) and at least part of the mounting portion (14, 16) comprise at least one material (M) overmoulded on at least part of the circuit substrate (20). The second region (24) of the circuit substrate (20) includes at least one restricted substrate portion (30), having a substrate width (Wr) smaller than the substrate width (W) of the sensing region (23). At least part of the at least one restricted substrate portion (30) extends axially in the mounting portion (16).