Inductive coupler with magnetic material

A semiconductor die, comprising:

• a semiconductor substrate;
• a transmitter or receiver circuit in the semiconductor substrate;
• a multi-layer stack on the semiconductor substrate, the multi-layer stack including a plurality of metallization layers separated from one another by an interlayer dielectric;
• a transformer in the multi-layer stack and electrically coupled to the transmitter or receiver circuit, the transformer including a first winding formed in a first metallization layer of the plurality of metallization layers and a second winding formed in a second metallization layer of the plurality of metallization layers, the first winding and the second winding being inductively coupled to one another;
• a magnetic material in the multi-layer stack and adjacent to at least part of the transformer;
• and
• a first guard ring designed to isolate electrical disturbances and as a diffusion barrier for preventing contaminants from propagating inward from an edge of the semiconductor die,
• wherein the first guard ring is formed from part of the metallization layers of the multi-layer stack and metal vias that extend between the metallization layers,
• wherein the magnetic material includes the second guard ring that laterally surrounds at least part of the transformer,
• wherein the second guard ring formed by the magnetic material merges or connects to the first guard ring.