Field effect transistor with vertical channel and preparation method thereof

The invention provides a field effect transistor with a vertical channel and a preparation method thereof. The preparation method comprises the following steps: S1, forming a fin structure on a substrate, wherein the bottom of the fin structure is provided with a first doping region; S2, forming a bottom side wall that surrounds and contacts the first doping region on the substrate; S3, forming agate stack structure that surrounds and contacts the fin structure on the bottom side wall, wherein the gate stack structure protrudes from the top of the fin structure; S4, forming a top side wall that surrounds and contacts the fin structure on the gate stack structure, and forming a second doping region on the fin structure, wherein at least part of the second doping region protrudes from the top side wall, and the first doping region and the second doping region form a source/drain electrode of the field effect transistor. The preparation method has the advantages of easing restrictions tophysical gate length and