A method for fabricating a semiconductor device comprises forming a nanowire on an insulator layer at a surface of a substrate; forming a dummy gate over a portion of the nanowire and a portion of the insulator layer; forming recesses in the insulator layer on opposing sides of the dummy gate; forming spacers on opposing sides of the dummy gate; forming source regions and drain regions in the recesses in the insulator layer on opposing sides of the dummy gate; depositing an interlayer dielectric on the source regions and the drain regions; removing the dummy gate to form a trench; removing the insulator layer under the nanowire such that a width of the trench underneath the nanowire is equal to or less than a distance between the spacers; and forming a replacement gate in the trench.