A semiconductor integrated circuit device with a buffer circuit is disclosed, which comprises a pre-buffer configured to receive an input signal from a front-stage circuit, a drive buffer having a first PMOS transistor and a first NMOS transistor connected in series between a power supply node and a ground node, the first PMOS and NMOS transistors having gates for receiving an output signal of the pre-buffer, a series-connection node of the first PMOS and NMOS transistors being connected to the output node, and a back-up buffer having a second PMOS transistor and a second NMOS transistor connected in series between the power supply node and the ground node, a series-connection node of the second PMOS and NMOS transistors being connected to the output node, one of the second PMOS and NMOS transistors is turned on after the other is turned off when the drive buffer is in a switching operation.