Patent ID: 8552522

Claim:
A circuit structure comprising: a semiconductor substrate; a first and a second conductive gate strips over the semiconductor substrate, wherein the first and the second conductive gate strips have a gap therebetween, and wherein the first and the second conductive gate strips comprise first top surfaces; a first inter-layer dielectric (ILD) in a gap between the first and the second conductive gate strips, wherein the first ILD comprises a second top surface lower than the first top surfaces, and wherein the second top surface is curved, with a center portion of the second top surface being lower than edge portions of the second top surface; and a second ILD over the first ILD, wherein the second ILD comprises a bottom surface contacting the second top surface, and a third top surface substantially coplanar with the first top surfaces, and wherein the second top surface and the bottom surface of the second ILD form a noticeable interface.