Semiconductor structure with multiple transistors having various threshold voltages
First Claim
1. A method of fabricating a semiconductor structure, comprising:
- concurrently implanting in a substrate a first screening region for each of first, second, and third transistor elements;
implanting in the substrate a second screening region above the first screening region for the second transistor element;
implanting in the substrate a third screening region above the first screening region for the third transistor element;
forming a substantially undoped epitaxial layer covering the first, second, and third screening regions to form a channel layer for each of first, second, and third transistor elements,wherein the first screening region is in contact with at least one of the second and third screening regions.
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Abstract
A semiconductor structure includes first, second, and third transistor elements each having a first screening region concurrently formed therein. A second screening region is formed in the second and third transistor elements such that there is at least one characteristic of the screening region in the second transistor element that is different than the second screening region in the third transistor element. Different characteristics include doping concentration and depth of implant. In addition, a different characteristic may be achieved by concurrently implanting the second screening region in the second and third transistor element followed by implanting an additional dopant into the second screening region of the third transistor element.
515 Citations
10 Claims
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1. A method of fabricating a semiconductor structure, comprising:
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concurrently implanting in a substrate a first screening region for each of first, second, and third transistor elements; implanting in the substrate a second screening region above the first screening region for the second transistor element; implanting in the substrate a third screening region above the first screening region for the third transistor element; forming a substantially undoped epitaxial layer covering the first, second, and third screening regions to form a channel layer for each of first, second, and third transistor elements, wherein the first screening region is in contact with at least one of the second and third screening regions. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification