Semiconductor device and manufacturing method thereof

A semiconductor device having a gate structure of an nMOS field-effect transistor, the semiconductor device comprising:

• a gate insulating layer formed on an inner wall of a substrate recess;
• a work function material layer formed on the gate insulating layer;
• and
• a gate metal formed on the work function material layer so as to apply a tensile stress to a channel of the nMOS field-effect transistor.

A method for manufacturing a semiconductor device, comprising:

• forming a gate insulating layer on an inner wall of a substrate recess of a MOS field-effect transistor;
• forming a work function material layer on the gate insulating layer;
• and
• depositing a gate metal on the work function material layer, wherein at least one of the forming of the work function material layer and the depositing of the gate metal applies a tensile or compressive stress to a channel of the MOS field-effect transistor.