Method for manufacturing semiconductor device
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Abstract
A trench-gate type transistor has a gate insulating film formed on an inner wall of a trench. The gate insulating film includes a first portion located on a wall of the trench and a second portion located on upper and bottom portions of the trench. The first portion includes a first oxide film, a nitride film, and a second oxide film. The second portion includes only an oxide film and is thicker than the first portion. Accordingly, electric field concentration on upper and lower corner portions of the trench can be reduced to improve the withstand voltage. In addition, and end of the trench may have an insulation layer that is thicker than the first portion.
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Citations
31 Claims
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1-17. -17. (canceled)
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18. A method for manufacturing a semiconductor device, comprising:
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preparing a semiconductor substrate having a trench formed thereon;
forming a first oxide film on an inner wall of the trench;
forming a nitride film on the first oxide film;
partially removing the nitride film so that the first oxide film is exposed at a first region of the inner wall and so that the nitride film remains on the first oxide film at a second region of the inner wall;
forming a second oxide film, by thermal oxidation, on the first oxide film at the first region and on the nitride film at the second region. - View Dependent Claims (19, 20, 21)
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22. A method for manufacturing a trench-gate type transistor, comprising:
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preparing a semiconductor substrate composed of a first conductivity type first semiconductor layer, a second conductivity type second semiconductor layer, and a first conductivity type third semiconductor layer;
forming a trench on the semiconductor substrate from a main surface of the semiconductor substrate at a side of the first semiconductor layer, the trench penetrating the first semiconductor layer and the second semiconductor layer to reach the third semiconductor layer;
forming a gate insulating film on an inner wall of the trench by forming a first oxide film on the inner wall of the trench;
forming a nitride film on the first oxide film;
removing a part of the nitride film to expose a part of the first oxide film; and
forming a second oxide film on the nitride film and on the part of the first oxide film; and
forming a gate electrode in the trench. - View Dependent Claims (23, 24, 25, 26)
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27. A method for manufacturing a trench-gate type transistor, comprising:
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a semiconductor substrate having a trench thereon; and
forming a gate insulating film on an inner wall of the trench, wherein the formation of the gate insulating film is comprising;
forming a first oxide film on the inner wall of the trench;
locally disposing an oxidation preventive film on the first oxide film; and
forming a second oxide film by thermal oxidation on the first oxide film with the oxidation preventive film locally interposed therebetween. - View Dependent Claims (28, 29, 30)
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31-57. -57. (canceled).
Specification