A method for the joining of ceramic pieces with a hermetically sealed joint comprising brazing a continuous layer of joining material between the two pieces. The wetting and flow of the joining material is controlled by the selection of the joining material, the joining temperature, the time at temperature, the joining atmosphere, and other factors. The ceramic pieces may be aluminum nitride and the pieces may be brazed with an aluminum alloy under controlled atmosphere. The joint material is adapted to later withstand both the environments within a process chamber during substrate processing, and the oxygenated atmosphere which may be seen within the shaft of a heater or electrostatic chuck.