Trench MOSFET having low gate charge

摘要

A trench MOSFET device comprising: (a) a silicon substrate of a first conductivity type (preferably N-type conductivity); (b) a silicon epitaxial layer of the first conductivity type over the substrate, the epitaxial layer having a lower majority carrier concentration than the substrate; (c) a body region of a second conductivity type (preferably P-type conductivity) within an upper portion of the epitaxial layer; (d) a trench having trench sidewalls and a trench bottom, which extends into the epitaxial layer from an upper surface of the epitaxial layer and through the body region of the device; (f) an oxide region lining the trench, which comprises a lower segment covering at least the trench bottom and upper segments covering at least upper regions of the trench sidewalls; (g) a conductive region within the trench adjacent the oxide region; and (h) a source region of the first conductivity type within an upper portion of the body region and adjacent the trench. The lower segment of the oxide region is thicker than the upper segments of the oxide region in this embodiment.