Photographic templates (masks) used to imprint three-dimensional images or patterns on layers of material in manufacturing semiconductor chips. Mask works may be protected in the US by rights (similar to copyrights (www.practicallaw.com/5-501-4872)) that are administered by the US Copyright Office (www.practicallaw.com/5-385-5776) under the authority of the federal Semiconductor Chip Protection Act of 1984 (www.practicallaw.com/9-504-3801) (SCPA).
A mask work must be registered with the US Copyright Office to secure protection under the SCPA (unlike copyrights, which are not necessarily registered). Though not required, notice of ownership may be affixed to a registered mask work and resulting semiconductor chips, which bars an accused infringer from raising the affirmative defense of innocent infringement.
For more information, see Practice Note, Intellectual Property: Overview: Mask Works (www.practicallaw.com/8-383-4565).