squeegee as a trench becomes thicker aspect ratio increases the trench cannot be sufficiently filled with a paste as a result a chip through plug having a void is formed an embodiment of the present invention which can solve the above problems that arise when the size width and depth of a trench is increased will be described below fig6 a to 6 e are sectional views showing the steps in a method of forming a chip through plug according to the fifth embodiment of the present invention in this embodiment a chip through plug is formed in a ceramic substrate first of all as shown in fig6 a a trench 12 having for example an opening diameter of 100 u03bcm and a depth of 200 u03bcm is formed in the surface of a ceramic substrate 11 having for example a width of 4 cm and a thickness of 0 8 mm thereafter the ceramic substrate 11 is calcined as shown in fig6 b a calcined conductive paste 13 having a thickness larger than the depth of the trench 12 is buried in the trench 12 by the burying method screen printing using the squeegee and a metal mask having an opening portion equal to or larger than the opening diameter of the trench 12 e.