. A MOSFET device, comprising:
a substrate, wherein the substrate includes an active region and a non-active region, and the substrate includes a plurality of trenches;
a plurality of shallow trench isolation structures, wherein the shallow trench isolation structures are in the trenches of the non-active region;
a thin insulating layer, formed in the trenches of the active region and over the surface of the substrate;
a multiple T-shaped gate layer, including a first part and a second part, wherein the first part is on the surface between two trenches, and the second part is in the trenches of the active region; and
a source/drain region, including a shallow doped region and a deep doped region, wherein the shallow doped region is in the substrate under the first part, and the deep doped region is in the substrate besides the second part;
wherein the deep doped region is deeper than the trenches, and the trenches are deeper than the shallow doped region.