Methods of fabricating semiconductor sensor devices include steps of fabricating a hermetically sealed MEMS cavity enclosing a MEMS sensor, while forming conductive vias through the device. The devices include a first semi-conductor layer defining at least one conductive via lined with an insulator and having a lower insulating surface; a central dielectric layer above the first semiconductor layer; a second semiconductor layer in contact with the at least one conductive via, and which defines a MEMS cavity; a third semiconductor layer disposed above the second semiconductor layer, and which includes a sensor element aligned with the MEMS cavity; a cap bonded to the third semiconductor to enclose and hermetically seal the MEMS cavity; wherein the third semiconductor layer separates the cap and the second semiconductor layer.