PURPOSE: To check specifications of the title semiconductor device such as an operating speed by easily finding a gate having any process failure by switching on and off test input and normal input switches based upon a control signal fed from a control line and changing the operation to a test mode.

CONSTITUTION: A basic single gate of a gate array comprises a two-input NAND gate 11 for example, which includes on one input side a test MOS transistor 12 and a normal input [1] MOS transistor 13 while including on the other input side a test MOS transistor 14 and a normal input [2] MOS transistor 15. The transistors 12, 14 are connected to a control line 1 while the transistors 13, 15 are connected to a control line 2. A given control signal is applied to the control lines 1, 2 to switch on and off transistors 12 to 15. Hereby, a gate having any process failure can easily be found to also check specifications such as an operating speed.