In this article, an analytical framework is put together to describe a pH Sensor based on Ion Sensitive Field-Effect Transistor (ISFET) and then simulated using Synopsys TCAD tool. In the proposed simulation work the electrolyte material and oxide surface charge density have been modeled explicitly by using experimental data available in the literature which makes this study unique from previously reported works. Furthermore, the method for adding a new material in Synopsys TCAD and using its advanced PMI feature are briefly illustrated in this work. The proposed work is validated against an available experimental work with good accuracy of 2.66% error percentage in the result. This article gives an adequate insight into the working principle of ISFET device with the objective of assisting beginners in this field before one can proceed into advanced research.