Semiconductor photonics device and methods of formation

A method, comprising:

• forming an optical modulator structure in a semiconductor layer above a first dielectric layer of a semiconductor photonics device;
• forming, above the first dielectric layer, a second dielectric layer that surrounds the optical modulator structure;
• forming an etch stop layer over the second dielectric layer and over the optical modulator structure, wherein the second dielectric layer resides directly on the etch stop layer;
• forming a first portion of a third dielectric layer over the etch stop layer;
• forming, above the optical modulator structure, a modulator heater structure in the first portion of the third dielectric layer;
• forming, above the first portion of the third dielectric layer and above the modulator heater structure, a second portion of the third dielectric layer and a plurality of dielectric layers;
• and
• forming an isolation trench through the plurality of dielectric layers, through the third dielectric layer, and to the etch stop layer,
• wherein the isolation trench surrounds the modulator heater structure in a top view of the semiconductor photonics device, and
• wherein the isolation trench has a rounded top view shape in the top view of the semiconductor photonics device.

A semiconductor photonics device, comprising:

• a substrate;
• one or more first dielectric layers over the substrate;
• an etch stop layer over the one or more first dielectric layers;
• a plurality of second dielectric layers over the etch stop layer, wherein a second dielectric layer, of the plurality of second dielectric layers, resides directly on the etch stop layer;
• an optical modulator structure in the one or more first dielectric layers;
• a modulator heater structure in one or more of the plurality of second dielectric layers,
• wherein the modulator heater structure is located above the optical modulator structure;
• and
• an isolated region of the plurality of second dielectric layers,
• wherein the isolated region of the plurality of second dielectric layers is located above the optical modulator structure,
• wherein the modulator heater structure is included in the isolated region of the plurality of second dielectric layers,
• wherein the isolated region of the plurality of second dielectric layers is isolated from other regions of the plurality of second dielectric layers by an isolation trench, and
• wherein the isolated region of the plurality of second dielectric layers has a ring top view shape in a top view of the semiconductor photonics device.