Semiconductor device having v-shaped region

A method for forming a semiconductor device, comprising:

• etching a region of a substrate ex-situ to form a u-shaped recess, the u-shaped recess extending into the substrate from a first substrate surface upon which a gate stack of the semiconductor device is formed;
• etching at least some of a sidewall defining the u-shaped recess in-situ to form a v-shaped recess, comprising:
• applying an etching gas to the sidewall to transform the u-shaped recess into the v-shaped recess;
• and
• epitaxially growing a stressed monocrystalline semiconductor material within the v-shaped recess.

A method for forming a semiconductor device, comprising:

• forming a u-shaped recess in a substrate;
• removing at least some native oxide from a sidewall that defines the u-shaped recess;
• and
• etching at least some of the sidewall in-situ after the removing to form a v-shaped recess in which at least one a source or a drain of a transistor is formed.