INTERATED CIRCUIT STRUCTURES AND METHODS FOR FORMING THE SAME

An integrated circuit structure includes a bulk semiconductor region, a first semiconductor strip over and connected to the bulk semiconductor region, and a dielectric layer including silicon oxide therein. Carbon atoms are doped in the silicon oxide. The dielectric layer includes a horizontal portion over and contacting a top surface of the bulk semiconductor region, and a vertical portion connected to an end of the horizontal portion. The vertical portion contacts a sidewall of a lower portion of the first semiconductor strip. A top portion of the first semiconductor strip protrudes higher than a top surface of the vertical portion to form a semiconductor fin. The horizontal portion and the vertical portion have a same thickness. A gate stack extends on a sidewall and a top surface of the semiconductor fin.