Organic semiconductor (OSC) gas sensors have grown into a widely discussed technology because of the presence of nanoscale fabrication processes. Thanks to the rapid development of nanotechnology, the performance of the OSC gas sensor has been pushed to the peak of its own and now can be used for numerous biomedical and environmental monitoring purposes that require high-precision sensing capability. However, the sophisticated and nonstandard fabrication process of most of these sensors has become the major impediment on the way of commercialization. Here, we demonstrate a micrometer-scale structure with a coupling layer using the current spreading effect to further enhance the sensing performance. The high-conductivity material poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS PH1000) was used as the coupling layer to increase the device operational current. The sensor exhibits a remarkably enhanced operational current of the microampere level without sacrificing the ammonia sensing capability. The issues of the structural profile are discussed carefully, and the sensor was tested with human breath samples to demonstrate a promising result. With the most common micrometer-scale fabrication technology, a ppb-regime sensing capability has been achieved, and the result of this work gives us a cut-in point regarding the high-sensitivity OSC gas sensors.