Abstract: A variable operation speed MOS transistor having a source, a drain and a gate with a plurality of contacts formed thereon. One end of the gate of the variable operation speed MOS transistor is connected to drains/sources of first MOS transistors, while the plurality of the contacts formed on the gate of the variable operation speed MOS transistor are connected to the drains/sources of second MOS transistors, which are of an opposite type to that of the first MOS transistors, and the source or drains of which are connected to Vcc. Input signals are supplied to the respective gates of the first and second MOS transistors in such a manner as to adjust the turn-on and turn-off speeds of the variable operation speed MOS transistor.