Methods of fabricating multigate transistors using dummy oxide interposers are disclosed herein. An exemplary method includes forming a multilayer stack that includes first semiconductor layers, sacrificial semiconductor layers, and a substrate extension. A source/drain recess is formed by removing the first semiconductor layers, sacrificial semiconductor layers, and a portion of the substrate extension in a source/drain region, and a source/drain structure is formed in the source/drain recess. The source/drain structure includes a second semiconductor layer and an insulator layer, and the insulator layer is disposed between the second semiconductor layer and the substrate extension. Before forming the source/drain structure, the sacrificial semiconductor layers are replaced with sacrificial dielectric layers. After forming the source/drain structure, the sacrificial dielectric layers are removed from a channel region to form a portion of a gate opening. A gate stack is formed in the portion of the gate opening.

The disclosure provides dyes for marking hydrocarbon compositions. More particularly, the disclosure relates to non-mutagenic dyes for marking hydrocarbon compositions.