This letter presents a novel complementary metal–oxide–semiconductor (CMOS)-compatible technique to fabricate a sub-100-nm slot waveguide in wafer-scale, which is beyond the resolution limit of conventional deep ultraviolet (DUV) lithography. We also demonstrate fabrication of an efficient channel-slot coupler with an ultrasharp tip by using slanted cutting.<?Pub _bookmark Command="[Quick Mark]"?> The propagation loss of the slot waveguide obtained is for the 100-nm slot and for the 80-nm slot, while each pair of channel-slot couplers has a very low insertion loss of . Finally, a Mach–Zehnder interferometer structure-based optical sensor demonstrates the integrate-ability of the proposed circuit.