A method for forming a nanogap includes forming a knockoff feature on a dielectric layer and forming a trench in the dielectric layer on opposite sides of the knockoff feature. A noble metal is deposited in the trenches and over the knockoff feature. A top surface is polished to level the noble metal in the trenches with a top of the dielectric layer to form electrodes in the trenches and to remove the noble metal from the knockoff feature. A nanochannel is etched into the dielectric layer such that the knockoff feature is positioned within the nanochannel. The knockoff feature is removed to form a nanogap between the electrodes.