A micromechanical inertial sensor includes an ASIC element having a processed front side, an MEMS element having a micromechanical sensor structure, and a cap wafer mounted above the micromechanical sensor structure, which sensor structure includes a seismic mass and extends over the entire thickness of the MEMS substrate. The MEMS element is mounted on the processed front side of the ASIC element above a standoff structure and is electrically connected to the ASIC element via through-contacts in the MEMS substrate and in adjacent supports of the standoff structure. A blind hole is formed in the MEMS substrate in the area of the seismic mass, which blind hole is filled with the same electrically conductive material as the through-contacts, the conductive material having a greater density than the MEMS substrate.