Abstract: A method of making a metal oxide semiconductor field effect transistor. An oxide layer is grown on the overall exposed surface of a substrate, which then has a trench formed by an etching process. A polysilicon layer is deposited on the trenched substrate, by using a nitride layer formed on the substrate as a mask, to form a gate region of a predetermined thickness. Then, the nitride layer is removed. The exposed portion of the polysilicon gate layer is then oxidized. Then, the exposed portion of the silicon substrate, disposed at opposite sides of the gate electrode, is subjected to a low concentration n-type ion injection, to form low concentration drain and source regions. Then, an oxide side wall is formed to surround the gate electrode. The exposed surface of the silicon substrate, disposed at opposite sides of the gate electrode, is subjected to a high concentration n-type ion injection.