Among various sensing technologies to detect magnetic field, the Hall effect is perhaps the most widespread and commonly used. Since it is possible to fabricate high quality hall effect transducers with the standard integrated circuit processes used in the microelectronics industry, and to integrate ancillary signal-processing circuitry on the same silicon die, usable sensors can be fabricated readily and inexpensively. In the field of scientific research, hall sensors have been extremely valuable tools for accurate measurement of magnetic fields in particle accelerators, characterizing superconductors, detecting and characterizing small magnetic particles, and so on. Whereas more than half a century has passed since the first time hall sensors were discovered, research about hall sensors is ongoing. In these research efforts different models, new applications according to new technologies, new materials or structures, and circuits are proposed to improve the performance of hall sensors. Designing good interface circuitry for a transducer requires that one understand how the transducer behaves. Carrier concentration, current density, geometry and so on describe the device from a physical standpoint, but what is needed is a model that describes how the device interacts with other components. In this thesis, a new model is studied according to hall sensor's structure and physics which describes behavior of sensor and its interaction with other circuit elements. In this model, almost all physical and structural parameters are considered, which are varied through design or fabrication processes. This model helps users or designers of hall sensors to choose the best fabrication process, structure and material depending on their application. Also, this model helps fabrication process designer to choose the best parameters for their process especially for hall sensors application. First of all, to obtain the best model for hall sensors, the basic features of sensors such as different parameters, defined about hall sensors, various materials, used to fabricate this kind of sensors, and different structures and geometries are studied. After that, influences of these parameters on the performance of hall sensor are investigated. For this purpose, Silvaco software is used. By using this software, the sample is described, magnetic field is focused on it and the hall voltage is measured. Moreover, sensitivity of hall sensor to different parameters can be measured with this software. In the next step, equations between hall voltage and these parameters are extracted. This step is done using MATLAB curve fitting toolbox for all of these physical and structural parameters. By using these equations a new model is proposed, which can be used by other circuit devices like transistors, resistors, op-amp and etc. This model is used to simulate hall sensors with a sample circuit. For this simulation, Hspice software is utilized. Some of those physical or structural parameters are chosen to simulate with Hspice and the model is tested. In the end, some structure's layouts are drawn with Cadence. These structures are chosen because some of them cannot be simulated with Silvaco and some of the other layouts are drawn to compare with simulation results. These layouts are sent to fabricate with 180 nm CMOS standard technology. Keywords 1- Magnetic sensors, 2- Hall sensors, 3- Modeling, 4- Hall sensors Applications