PURPOSE: To relieve the application of stress to a ceramic board on the bottom of a cavity generated between a semiconductor chip and a cavity side wall without expanding the size of a package by installing a horizontal groove to the side wall on the bottom of a device-mount cavity installed in a package and expanding the opening dimensions of said cavity bottom.

CONSTITUTION: A semiconductor chip 1 is installed to a cavity 4 in the inner- sided central part of a ceramic vessel 2 by a mount material 9. The bottom 12 of this cavity 4 is larger than the size of an opening section 13 on the upper part where a horizontal groove 5 is provided on a side wall 11 of the cavity horizontally. The depth of the horizontal groove 5 is determined by the sizes of the semiconductor chip 1, the ceramic vessel 2, and the cavity 4. More importantly, it is determined by the wall thickness of the cavity bottom, and the distance between the terminal section of the semiconductor chip 1 and the side wall of the cavity.