Abstract: Provided are high voltage metal oxide semiconductor field effect transistor (HVMOSFET) having a Si/SiGe heterojunction structure and method of manufacturing the same. In this method, a substrate on which a Si layer, a relaxed SiGe epitaxial layer, a SiGe epitaxial layer, and a Si epitaxial layer are stacked or a substrate on which a Si layer having a well region, a SiGe epitaxial layer, and a Si epitaxial layer are stacked is formed. For the device having the heterojunction structure, the number of conduction carriers through a potential well and the mobility of the carriers increase to reduce an on resistance, thus increasing saturation current. Also, an intensity of vertical electric field decreases so that a breakdown voltage can be maintained at a very high level. Further, a reduction in vertical electric field due to the heterojunction structure leads to a gain in transconductance (Gm), with the results that a hot electron effect is inhibited and the reliability of the device is enhanced.