Method of forming a gate dielectric by in-situ plasma

A method of forming a gate dielectric layer includes forming a first dielectric layer over a semiconductor substrate using a first plasma, performing a first in-situ plasma nitridation of the first dielectric layer to form a first nitrided dielectric layer, forming a second dielectric layer over the first dielectric layer using a second plasma, performing a second in-situ plasma nitridation of the second dielectric layer to form a second nitrided dielectric layer; and annealing the first nitrided dielectric layer and the second nitrided dielectric layer, wherein the gate dielectric layer comprises the first nitrided dielectric layer and the second nitrided dielectric layer. In other embodiments, the steps of forming a dielectric layer using a plasma and performing an in-situ plasma nitridation are repeated so that more than two nitrided dielectric layers are formed and used as the gate dielectric layer.