In this paper, the effect of High K dielectric layer on Silicon based Metal-oxide-semiconductor field-effect transistors (MOSFETs) was studied. As we know MOSFET place a very important role in modern electronics, this work investigates the relationship between drain current and gate voltage in MOSFETs with different High K dielectric materials. The dielectric layer in MOSFETs separates the gate electrode from the semiconductor channel, controlling the flow of current through the device. Silicon dioxide (SiO2) has historically been the dielectric of choice due to its excellent insulating properties and compatibility with silicon technology. However, as transistor dimensions shrink and performance demands increase, alternative dielectrics with higher permittivity (high-k dielectrics) have gained more prominence. Consequently, MOSFETs employing high-k dielectrics exhibit enhanced performance characteristics, including lower threshold voltages and higher drain currents at equivalent gate voltages compared to SiO2 based MOSFETs. To understand the dielectric properties of different High-k materials, gate voltage, and drain current is essential for optimizing the MOSFET performance. In this work Al2O3, HfSiO4, and HfO2 which has high dielectric constant than SiO2 were used to study the MOSFET performance. The HfO2 dielectric layer shows more current then the remaining dielectric layers.