A microphone and its manufacturing method, relating to semiconductor techniques. The microphone comprises a substrate with a back through-hole going through the substrate; a first electrode layer on the substrate covering the back through-hole; a back plate on the substrate, wherein the back plate and the first electrode layer form a cavity, and the first electrode layer comprises a gap connecting the back through-hole and the cavity; and a second electrode layer in the cavity and on a bottom surface of the back plate. In this inventive concept, the gap in the first electrode layer increases the sensitivity of the first electrode layer and thus improves the Signal-to-Noise Ratio (SNR).