At least one semiconductor nanowire laterally abutted by a pair of semiconductor pad portions is formed over an insulator layer. Portions of the insulator layer are etched from underneath the at least one semiconductor nanowire such that the at least one semiconductor nanowire is suspended. A temporary fill material is deposited over the at least one semiconductor nanowire, and is planarized to physically expose top surfaces of the pair of semiconductor pad portions. Trenches are formed within the pair of semiconductor pad portions, and are filled with stress-generating materials. The temporary fill material is subsequently removed. The at least one semiconductor nanowire is strained along the lengthwise direction with a tensile strain or a compressive strain.