Trench MOSFET and manufacturing method therefor

A trench metal-oxide-semiconductor field effect transistor (MOSFET), comprising:

• an epitaxial layer of a first dopant type;
• a first trench, extending from an upper surface of the epitaxial layer into the epitaxial layer;
• a first shield gate dielectric layer, arranged at a lower part of the first trench and covering an inner surface of the lower part of the first trench;
• a first shielding conductor, arranged at the lower part of the first trench and separated from the epitaxial layer by the first shield gate dielectric layer;
• a first dielectric interlayer, arranged on a surface of the first shield gate dielectric layer;
• a first gate dielectric layer, arranged at an upper part of the first trench and covering an inner surface of the upper part of the first trench;
• a first gate conductor, arranged at the upper part of the first trench and separated from the epitaxial layer by the first gate dielectric layer;
• a second trench, extending from the upper surface of the epitaxial layer into the epitaxial layer;
• a second shield gate dielectric layer, arranged at a lower part of the second trench and covering an inner surface of the lower part of the second trench;
• a second shielding conductor, arranged at the lower part of the second trench and separated from the epitaxial layer by the second shield gate dielectric layer;
• a second dielectric interlayer, arranged on a surface of the second shield gate dielectric layer;
• a second gate dielectric layer, arranged at an upper part of the second trench and covering an inner surface of the upper part of the second trench;
• a second gate conductor, arranged at the upper part of the second trench and separated from the epitaxial layer by the second gate dielectric layer;
• a body region, a source region, and a contact region, located on two sides in the epitaxial layer adjacent to the first trench and the second trench, wherein the source region is of the first dopant type, and the body region and the contact region are of a second dopant type;
• and
• a dielectric constant of the second gate dielectric layer located in the second trench is greater than that of the first gate dielectric layer located in the first trench.