A microelectromechanical (MEMS) device is fabricated from a wafer having a plurality of die regions with grooves and MEMS components formed on a wafer surface at each die region. A first metal having a relatively high melting temperature is formed on sidewalls of each groove, and a cap is attached at each die region to provide a closed cavity which encloses the grooves and MEMS components. Bottoms of the grooves are opened by thinning the wafer thereby establishing through-hole vias extending through the wafer at each die region, for accessing the cavity for inserting or removing material. The vias are sealed by interacting a second metal having a relatively low melting temperature with the first metal layer to form intermetallic compounds with higher melting temperature that maintain the seal during subsequent lower temperature operations.