Patent ID: 7618843

Claim:
A method of fabricating a multilayer ceramic substrate having a cavity comprising: preparing a previously fired ceramic substrate; stacking an unfired ceramic greensheet on the previously fired ceramic substrate, the unfired ceramic greensheet having an opening and having a firing temperature substantially equal to or lower than a firing temperature of the previously fired ceramic substrate, wherein a part of the surface of the previously fired ceramic substrate forms a bottom part of the cavity and the inside part of the opening of the unfired ceramic greensheet forms an inside wall of the cavity; stacking a restricting greensheet on the unfired ceramic greensheet, the restricting greensheet having a higher firing temperature than the unfired ceramic greensheet; firing the stack at the firing temperature of the unfired ceramic greensheet with or without pressure applied via the restricting greensheet while the stack is under restriction by the restricting greensheet; and eliminating the restricting greensheet after firing step, wherein the firing temperature of the unfired ceramic greensheet is lower than the firing temperature of the previously fired ceramic substrate.