Abstract: A method of fabricating a ceramic package body for holding semiconductor devices which include external terminals arranged on an outer surface of the ceramic package body, a first conductive pattern having first conductors connected respectively to the external terminals, and a second conductive pattern having second conductors not connected to any said external terminal.

Abstract: A semiconductor ceramic package includes a plurality of laminated insulator layers each formed from a ceramic. A semiconductor chip mounting portion is formed on a surface insulator layer. A power plane is formed on at least one of internal insulator layers. A ground plane is also formed on at least one of internal insulator layers. A plurality of thermal vias are formed beneath the semiconductor chip mounting portion. Each thermal via includes a first thermal via formed so as to transmit heat generated by a semiconductor chip mounted on the semiconductor chip mounting portion to the side of a back surface layer and a second thermal via formed so as to transmit the heat generated by the semiconductor chip to the side of the back surface layer. The first thermal via is connected to the power plane and the second thermal via is connected to the ground plane. The first and second thermal vias are formed to be adjacent to each other.