The present disclosure discloses a method for manufacturing an oxide layer and a semiconductor device, which pertain to the field of semiconductor technology. The method for manufacturing the oxide layer includes: providing a semiconductor structure; forming a first oxide layer on the semiconductor structure in a first low-temperature environment; applying an oxygen plasma treatment on the first oxide layer and a part of the semiconductor structure in a second low-temperature environment, so that the first oxide layer is formed into a second oxide layer, where a compactness of the second oxide layer is greater than a compactness of the first oxide layer. The semiconductor device includes a semiconductor structure and a second oxide layer disposed on the semiconductor structure, where the second oxide layer is manufactured and formed using the aforementioned oxide layer fabrication method.

A semiconductor structure includes a channel region over a substrate, a gate structure engaging the channel region, a gate spacer disposed on sidewalls of the gate structure, a source/drain (S/D) feature abutting the channel region, an S/D contact landing on a top surface of the S/D feature, and a dielectric layer disposed on a sidewall of the gate spacer. The S/D feature includes a first layer and a second layer underneath the first layer. The second layer differs from the first layer in composition. The dielectric layer interfaces with both the first layer and the second layer of the S/D feature. In a cross-sectional view along a lengthwise direction of the channel region, a bottommost point of the top surface of the S/D feature is below a top surface of the channel region.

An etching method according to one embodiment of the present disclosure includes step (a), step (b), step (c), step (d), and step (e). Step (a) provides a substrate that has a silicon-containing film which does not include oxygen and nitrogen, and a mask formed on the silicon-containing film. Step (b) etches the silicon-containing film with plasma generated from a first processing gas that includes a halogen-containing gas to form a recess portion. Step (c) forms an oxide film in the recess portion with plasma generated from a second processing gas that includes an oxygen-containing gas and a gas including carbon, hydrogen, and fluorine. Step (d) further etches the silicon-containing film with the plasma generated from the first processing gas after step (c). Step (e) repeatedly executes step (c) and step (d) a preset number of times.