PURPOSE: To improve a MOS transistor in switching characteristics by a method wherein the transistor is changed in gate length.

CONSTITUTION: A gate 2 different from that of a conventional MOS transistor in structure is formed large in gate length near a gate electrode and becomes gradually smaller in gate length as receding from the gate electrode. When an input voltage is applied onto the gate 2 and changed, the gate 2 changes in voltage starting from its part near the electrode due to the resistance and the distributed capacity of the gate 2. As the gate 2 is large in gate length near the electrode, a drain current is small in displacement near the electrode and large at a part distant from the electrode. As the load of an integrated circuit composed of MOS transistors is mainly composed of a capacitive load, the voltage of a drain changes as shown by a solid line. A drain changes in voltage as shown by a dotted line when a gate is short and constant in gate length. Judging from the waveform of a solid line, the solid line indicates that a drain is smaller in voltage change per unit time when a gate of this design is used as compared with a dotted line which indicates that a conventional gate is employed. Therefore, noises due to the change of a drain current can be lessened. A drain voltage can be changed in waveform by changing the gate 2 in gate length or in shape.