An integrated circuit includes a substrate, at least one n-type semiconductor device, and at least one p-type semiconductor device. The n-type semiconductor device is present on the substrate. The n-type semiconductor device includes a gate structure having a bottom surface and at least one sidewall. The bottom surface of the gate structure of the n-type semiconductor device and the sidewall of the gate structure of the n-type semiconductor device intersect to form an interior angle. The p-type semiconductor device is present on the substrate. The p-type semiconductor device includes a gate structure having a bottom surface and at least one sidewall. The bottom surface of the gate structure of the p-type semiconductor device and the sidewall of the gate structure of the p-type semiconductor device intersect to form an interior angle smaller than the interior angle of the gate structure of the n-type semiconductor device.