A complimentary metal-oxide-semiconductor (CMOS) circuit including: a substrate; and a plurality of field-effect transistors on the substrate. Each of the field-effect transistors includes: a plurality of contacts; a source connected to one of the contacts; a drain connected to another one of the contacts; a gate; and a spacer between the gate and the contacts. The spacer of one of the field-effect transistors has a larger airgap than the spacer of another one of the field-effect transistors.
