Manufacturing process of a microelectromechanical system with multiple cavities at different pressures and related microelectromechanical system

A process for manufacturing a microelectromechanical system starting from a first semiconductive wafer comprising a semiconductive substrate, a semiconductive region and a dielectric region interposed between the semiconductive substrate and the semiconductive region, the semiconductive region being delimited by a surface, said process comprising:

• forming a first cavity and a second cavity which extend into the semiconductive region starting from the surface and are laterally offset;
• forming a first channel which extends through the semiconductive region starting from the surface to a corresponding portion of the dielectric region, wherein said first channel is laterally offset with respect to the first cavity and the second cavity;
• successively selectively removing said portion of the dielectric region to form an intermediate chamber which extends between the semiconductive substrate and the semiconductive region and is laterally delimited by corresponding portions of the dielectric region and in communication with the first channel;
• mechanically coupling the first semiconductive wafer to a second semiconductive wafer, wherein a first microelectromechanical structure and a second microelectromechanical structure are formed, in such a way that the first cavity and the second cavity form respectively a first chamber and a second chamber, the second chamber being hermetically closed and having therewithin a pressure equal to a second chamber value, the first microelectromechanical structure and the second microelectromechanical structure extending respectively in the first chamber and the second chamber in such a way as to form a transversal channel which is delimited by the semiconductive region and by the second semiconductive wafer and which places the first chamber in communication with the first channel and the intermediate chamber;
• forming second channels which extend through the semiconductive substrate to the intermediate chamber to place the first chamber in communication with the outside;
• and
• setting a pressure in the first chamber equal to a first chamber value and hermetically closing the second channels, to hermetically close the first chamber, the transversal channel, the first channel and the intermediate chamber.