A semiconductor structure and a method for forming the same are provided. The method includes forming a gate structure over a substrate and forming source and drain regions adjacent to the gate structure. The method also includes forming a first ILD layer surrounding the gate structure over the source and drain regions and forming a contact modulation structure over the gate structure. The method also includes etching the first ILD layer and the contact modulation structure to form a first contact trench over the source and drain regions and a second contact trench over the gate structure. The method further includes forming a first contact in the first contact trench and a second contact in the second contact trench. In addition, the first ILD layer has a first etching rate and the contact modulation structure has a second etching rate that is less than the first etching rate.