Trench isolation gate device and fabricating method thereof

Abstract

The invention relates to a method of fabricating a trench isolation gate device. The method comprises steps: a semiconductor substrate is etched to form a trench; an oxide is deposited in the trench to form a floating gate oxide layer, the floating gate oxide layer is gradually thickened from top to bottom along the side wall of the trench, and the thickness of the floating gate oxide layer at thelower part of the side wall of the trench is the same as that of the floating gate oxide layer at the bottom part of the trench; polysilicon is deposited in the trench to form a floating gate polycrystalline layer; an insulating medium grows on the upper surface of the floating gate polycrystalline layer to form an isolation layer; and a control gate is formed on the isolation layer in the trench. A deposition technology is adopted to deposit the floating gate oxide layer at the bottom part of the trench, the floating gate oxide layer is gradually thickened from the side wall of the trench tothe bottom of the trench, and the thickness of the floating gate oxide layer at the lower part of the side wall of the trench is the same as that of the floating gate oxide layer at the bottom part of the trench. The gradually-changing floating gate oxide layer thickness can narrow the width of the trench, the cell area is further reduced, and the specific on-resistance of the device is reduced.

Description

technical field [0001] The present application relates to the technical field of semiconductor manufacturing, in particular to a trench separated gate device and a manufacturing method thereof. Background technique [0002] Since the split gate device structure was proposed, due to the advantages of the split gate structure such as low resistance and low gate capacitance, medium and low voltage ordinary trench VDMOS (Vertical Double-diffused Metal-Oxide-Semiconductor Field-Effect Transistor, vertical double-diffused metal-oxide semiconductor field Effect transistor) products are gradually being replaced by trench separated gate VDMOS devices. [0003] At present, the oxide layer in the lower part of the trench is realized by thermal oxidation growth or a thin oxide layer grown by thermal oxidation, and then a furnace tube oxidation method or deposition method is used to grow an oxide layer on the surface of the thin oxide layer. For the oxide layer grown by the above method...

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Problems solved by technology

[0004] Based on this, it is necessary to provide a trench separated gate device and a manufacturing method thereof in view of the problem in the prior art that the ratio of the oxide layer thickness at the bottom of the trench to the thickness of the trench sidewall oxide layer is small resulting in a large chip area.

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