A semiconductor fabrication process according to the present invention defines an auxiliary structure with a plurality of spaces with a predetermined line-width in the oxide layer to prevent the conductive material in the spaces from being removed by etching or defined an auxiliary structure to rise the conductive structure so as to have the conductive structure being exposed by chemical mechanical polishing. Thus, the transmitting circuit can be defined without requiring an additional mask. Hence, the semiconductor fabrication process can reduce the number of required masks to lower the cost.