Mullite ceramics were developed for multilayered packages, which have a lower dielectric constant and a nearer thermal expansion to that of silicon than those of alumina. The multilayered mullite packages are manufactured by using a similar cofired technology with tungsten or molybdenum to the conventionally used alumina system. A new brazing material and a new lead material were developed to be combined with the mullite ceramics Multilayered mullite packages with a brazed aluminum nitride heat sink, which has a high thermal conductivity, were developed to compensate a low thermal conductivity of the mullite itself. The packages are one of the highest performance packages.