Spacer Structure For Nano-Sheet-Based Devices

A method, comprising:

• receiving a structure of a semiconductor device, wherein the structure includes a stack of a first semiconductor layer over a semiconductor substrate, a second semiconductor layer over the first semiconductor layer, and a third semiconductor layer over the second semiconductor layer, wherein the first and the third semiconductor layers each includes a first semiconductor material, the second semiconductor layer includes a second semiconductor material, and the second semiconductor material is different from the first semiconductor material;
• etching a first trench in a first region of the stack and a second trench in a second region of the stack, the first and the second trenches each exposing a side surface of the first, the second, and the third semiconductor layers;
• after forming the first trench and the second trench, removing a first portion of the first semiconductor layer to form first gaps and a second portion of the third semiconductor layer to form second gaps;
• forming a first spacer in the first gaps and a second spacer in the second gaps,
• wherein the first portion has a first width along a first direction connecting the first and the second trenches, the second portion has a second width along the first direction, and the first width being greater than the second width.

A method, comprising:

• receiving a semiconductor structure having a stack of semiconductor layers formed thereon, the stack of semiconductor layers including a first semiconductor layer having a first thickness on a semiconductor substrate, a second semiconductor layer having a second thickness on the first semiconductor layer, and a third semiconductor layer having a third thickness on the second semiconductor layer, the first semiconductor layer has a first concentration of a first semiconductor material component, the third semiconductor having a second concentration of the first semiconductor material component, and the second semiconductor layer having a second semiconductor material component different from the first semiconductor material component;
• forming a trench in the stack of semiconductor layers to expose a first sidewall of the first semiconductor layer, a second sidewall of the second semiconductor layer and a third sidewall of the third semiconductor layer;
• etching the first and the third semiconductor layers through the exposed first and third sidewalls, respectively to form a fourth sidewall of the first semiconductor layer and a fifth sidewall of the third semiconductor layer;
• forming a first spacer on the fourth sidewall and between the second semiconductor layer and the substrate, and a second spacer on the fifth sidewall and on a top surface of the second semiconductor layer,
• wherein the first concentration differs from the second concentration or the first thickness differs from the third thickness, and
• wherein the first spacer has a first size, the second spacer has a second size, and the first size is greater than the second size.