PURPOSE: To preserve stored information of an ultraviolet ray erasable PROM without using a light shielding seal by providing a socket at the ultraviolet ray transmitting window side of a package, and mounting other IC element over the window at the socket.

CONSTITUTION: An ultraviolet ray transmitting window 4 is formed on the upper surface of a package 3 which contains an IC chip 2. Several terminal pins 5 are arranged on the side face of the package 3, and connected to the chip 2. A pair of sockets 6 connected to the chip 2 are oppositely arranged at both sides of the window 4. The terminal pins 9 at both side faces of the package 8 of an MOS- ROM7 are inserted into the sockets 6, and the ROM7 is disposed above the window 4 of the package 3. A packing 10 is provided between the packages 8 and 3 to prevent the external light from entering to the window 4. The information of the ROM1 can be erased by emitting strong ultraviolet ray from the window 4 by removing the RAM. According to this structure, the information of the ROM7 can be preserved without bonding a light shielding seal on the window 4.