Method for forming a semiconductor device having a strained channel and a heterojunction source/drain

A method for forming a transistor, comprising:

• providing a semiconductor layer;
• providing a gate dielectric overlying a first portion of the semiconductor layer;
• providing a gate electrode overlying the gate dielectric;
• encapsulating the gate electrode and the gate dielectric with a dielectric layer;
• selectively growing a semiconductor material overlying a second portion of the semiconductor layer outside the first portion, wherein the semiconductor material comprises a material different from a material of the semiconductor layer;
• oxidizing the semiconductor material in an oxygen ambient to form a stressor layer from the second portion of the semiconductor layer thereby forming a strained channel within the first portion of the semiconductor layer;
• and
• forming source and drain regions in the second portion of the semiconductor layer and the semiconductor material.

A method for forming a transistor, comprising:

• providing a semiconductor layer;
• providing a gate dielectric overlying a first portion of the semiconductor layer;
• providing a gate electrode of the transistor overlying the gate dielectric;
• encapsulating the gate electrode and the gate dielectric;
• selectively growing a semiconductor material containing germanium overlying a second portion of the semiconductor layer outside the first portion, wherein the semiconductor material comprises a material different from a material of the semiconductor layer;
• heating the semiconductor material to diffuse germanium into the second portion of the semiconductor layer thereby forming a strained channel underlying the gate dielectric;
• and
• forming source and drain regions of the transistor in the second portion of the semiconductor layer and the semiconductor material.