METHOD OF MANUFACTURING SEMICONDUCTOR DEVICES AND SEMICONDUCTOR DEVICES

In a method of manufacturing a semiconductor device, a fin structure is formed by patterning a semiconductor layer, an isolation insulating layer is formed such that an upper portion of the fin structure protrudes from the isolation insulating layer, a gate dielectric layer is formed by a deposition process, a nitridation operation is performed on the gate dielectric layer, and a gate electrode layer is formed over the gate dielectric layer. The gate dielectric layer as formed includes silicon oxide, and the nitridation operation comprises a plasma nitridation operation using a N2 gas and a NH3 gas.