Micro Electro Mechanical Systems (MEMS) based Ultrasonic Transducers presents several advantages for some applications such as ease of array fabrication, unique thermal manipulation capabilities. Micromachining allows us to miniaturize device dimensions and produce capacitive transducers whose performance is comparable with their piezoelectric counterpart. Computer simulation has been widely used for MEMS based system. The main advantage of computer simulation is to provide design optimization by varying geometry, layer dimension and materials of the device without actual fabrication. This systematic approach can save time and cost of device fabrication and experimentation. In this work, a model of Capacitive Micromachined Ultrasonic Transducer (CMUT) is simulated in COVENTORWARE software. The solver is used to analyze the electrical current flow, voltage and heat and stress distribution in the device. The result is used to predict the temperature and stress as a function of the applied voltage across heating layer. The displacement results are used in the mechanical analysis to predict the mechanical behaviour of the CMUT. Here two different types of dielectric materials Si3N4 and Zr02 are used. The optimization is performed mainly based on resonant frequency and collapse voltage. Then we use this model as a gas detector (Sensor) to detect gas like Methane.