The design, simulation and fabrication of a mass-sensitive CMOS-MEMS resonator are presented in this paper. The principle of detection of the gaseous species is based on the change in resonant frequency of the microresonator as a result of the absorption/adsorption of an analyte molecule onto the surface of the active material deposited on the microresonator resulting into a change of the mass of the microresonator device. CoventorWare simulation software is used to design and simulate the micromachined resonator gas sensing platform/membrane. From simulation, the resonant frequency of the resonator is found to be 6.45 kHz and 23 kHz for mode 1 and mode 2 (in y and z direction), respectively. The frequency decreases with increasing mass added on top of the CMOS-MEMS resonator membrane and the mass sensitivity of the resonator determined to be 0.18 Hz/pg. © 2012 IFSA.