In a semiconductor device of the Dual In-line Plug-in Package type, input terminals for receiving, for example, key input signals derived from key input means are aligned on a side of the semiconductor device, and output terminals for developing, for example, driving signals for display means are aligned on another side of said semiconductor device. The input terminals and the output terminals function, in combination, not only to electrically connect the key input means, the semiconductor device and the display means with one another, but also to mechanically connect a circuit board for supporting the key input means and another circuit board for supporting the display means with each other.