A method of fabricating an ultrasound device, the method comprising: providing a first wafer having a first silicon device layer with a first thickness and a dielectric layer with a second thickness in contact with the first silicon device layer, providing a second wafer having a second silicon device layer (310, 810), forming, in the first wafer, a plurality of cavities (1802, 806) by completely etching through the second thickness of the dielectric layer and by partially etching through the first thickness of the first silicon device layer; and bonding the second wafer with the first wafer so that the plurality of cavities (1802, 806) are disposed between the first silicon device layer and the second silicon device layer (310, 810), wherein forming, in the first wafer, a plurality of cavities (1802, 806) comprises, for each one of the plurality of cavities (1802, 806): forming an outer cavity portion by completely etching through the second thickness of the dielectric layer and partially etching through the first thickness of the first silicon device layer; and forming an inner cavity portion by etching portions of the dielectric layer bounded by the outer cavity portion down to the surface of the first silicon device layer, so that the outer cavity portion is adjacent to and surrounds the inner cavity portion, the outer cavity portion having a greater depth than the inner cavity portion, and the first silicon device layer is configured as a membrane of the plurality of cavities (1802, 806) of the ultrasound device. providing a first wafer having a first silicon device layer with a first thickness and a dielectric layer with a second thickness in contact with the first silicon device layer, providing a second wafer having a second silicon device layer (310, 810), forming, in the first wafer, a plurality of cavities (1802, 806) by completely etching through the second thickness of the dielectric layer and by partially etching through the first thickness of the first silicon device layer; and bonding the second wafer with the first wafer so that the plurality of cavities (1802, 806) are disposed between the first silicon device layer and the second silicon device layer (310, 810), wherein forming, in the first wafer, a plurality of cavities (1802, 806) comprises, for each one of the plurality of cavities (1802, 806): forming an outer cavity portion by completely etching through the second thickness of the dielectric layer and partially etching through the first thickness of the first silicon device layer; and forming an inner cavity portion by etching portions of the dielectric layer bounded by the outer cavity portion down to the surface of the first silicon device layer, so that the outer cavity portion is adjacent to and surrounds the inner cavity portion, the outer cavity portion having a greater depth than the inner cavity portion, and forming an outer cavity portion by completely etching through the second thickness of the dielectric layer and partially etching through the first thickness of the first silicon device layer; and forming an inner cavity portion by etching portions of the dielectric layer bounded by the outer cavity portion down to the surface of the first silicon device layer, so that the outer cavity portion is adjacent to and surrounds the inner cavity portion, the outer cavity portion having a greater depth than the inner cavity portion, and the first silicon device layer is configured as a membrane of the plurality of cavities (1802, 806) of the ultrasound device.