A signal transmission circuit of a semiconductor device includes a first emphasis circuit and a second emphasis circuit. The first emphasis circuit feeds a signal of an output node back to an input node. The first emphasis circuit may perform a first emphasis operation on a signal of the input node and the signal of the output node by adjusting a feedback time of the first emphasis circuit. The second emphasis circuit may be connected in parallel with the first emphasis circuit to perform a feedback of the signal of the output node to the input node. The second emphasis circuit may perform a second emphasis operation on the signal of the input node and the signal of the output node by adjusting a feedback time of the second emphasis circuit.