Methods are disclosed to fabricate a transistor, for example a FinFET, by forming over a substrate at least one electrically conductive channel between a source region and a drain region; forming a gate structure to be disposed over a portion of the channel, the gate structure having a width and a length and a height defining two opposing sidewalls of the gate structure and being formed such that the channel said passes through the sidewalls; forming spacers on the sidewalls; forming a layer of epitaxial silicon over the channel; removing the spacers; and forming a dielectric layer to be disposed over the gate structure and portions of the channel that are external to the gate structure such that a capacitance-reducing air gap underlies the dielectric layer and is disposed adjacent to the sidewalls of said gate structure in a region formerly occupied by the spacers.