A method of fabricating a semiconductor integrated circuit (IC) is disclosed. A dielectric layer is formed over a substrate. An interlayer is formed over the dielectric layer. A first photoresist layer with a first opening is formed over the interlayer and a second photoresist layer having a second opening is formed over the first photoresist layer. Spacers are formed along sidewalls of the first opening and the second opening. A first trench is formed in the interlayer by using the spacer along the first opening as an etch mask. A second trench is formed in the interlayer by using the spacer along the second opening as an etch mask. The first trench and the second trench are extended down into the dielectric layer as a lower portion and an upper portion, respectively, of a dielectric trench.