Semiconductor device and manufacturing method thereof

Abstract

A semiconductor device includes a substrate, a shallow trench isolation structure, two epitaxial structures, one or more semiconductor channel layers, a gate metal layer and a gate spacer. The shallow trench isolation structure is disposed over the substrate. The epitaxial structures are disposed over the shallow trench isolation structure. The one or more semiconductor channel layers connect the two epitaxial structures. The gate metal layer is located between the epitaxial structures and engages the one or more semiconductor channel layers. The gate spacer is in contact with a sidewall of the gate metal layer. From a cross-section view, a neck portion of the gate metal layer adjacent to and along the one or more semiconductor channel layers, and one side of the neck portion is retracted by a distance relative to the gate spacer, and the distance is greater than 0 and less than or equal to 2 nanometers.