Stacked multi-gate device with diffusion stopping layer

A device, comprising:

• a bottom transistor comprising:
• a first channel layer extending along a first direction;
• a first gate structure across the first channel layer and extending along a second direction different from the first direction;
• and
• first source/drain structures on opposite sides of the first channel layer, wherein a height of the first source/drain structures and a width of the first source/drain structures are different;
• a top transistor over the bottom transistor and comprising:
• a second channel layer;
• a second gate structure across the second channel layer;
• and
• second source/drain structures on opposite sides of the second channel layer;
• and
• a dielectric structure between the bottom transistor and the top transistor, the dielectric structure comprising a first dielectric layer over the first source/drain structures and a second dielectric layer over the first dielectric layer, wherein the second source/drain structures are over the second dielectric layer, and at least one of the first dielectric layer and the second dielectric layer has diffusion-blocking dopants.

A device, comprising:

• a bottom transistor comprising:
• a first gate structure comprising a gate dielectric layer and a metal layer comprising a titanium-containing material;
• a first channel structure embedded in the first gate structure;
• and
• first source/drain structures connected to the first channel structure;
• a top transistor comprising:
• a second gate structure;
• a second channel structure embedded in the second gate structure;
• and
• second source/drain structures connected to the second channel structure;
• a semiconductive layer between the first source/drain structures and the second source/drain structures, the semiconductive layer comprising a first epitaxial layer with first diffusion-blocking dopants over the first source/drain structures and a second epitaxial layer over the first epitaxial layer;
• a contact etch stop layer over the second source/drain structures;
• and
• an interlayer dielectric layer over the contact etch stop layer.