Semiconductor device and method for forming the same

A semiconductor device, comprising:

• a semiconductor substrate;
• a gate structure disposed on the semiconductor substrate, wherein the gate structure comprises:
• a gate dielectric layer;
• and
• a gate electrode formed on the gate dielectric layer, wherein the gate dielectric layer comprises nitrogen ions so that a lower portion of the gate dielectric layer comprises positive charges;
• a sidewall spacer disposed on sidewalls of the gate structure;
• a lightly doped source/drain region formed in the semiconductor substrate on opposite sides of the gate structure;
• a source/drain region formed in the semiconductor substrate on opposite sides of the sidewall spacer;
• a halo implant region formed in the semiconductor substrate below the gate structure and adjacent to the lightly doped source/drain region, wherein the halo implant region is spaced apart from the source/drain region by a portion of the semiconductor substrate;
• and
• a counter-doping region formed in the semiconductor substrate below the gate structure and between the lightly doped source/drain region and the halo implant region, the counter-doping region extending into the semiconductor substrate directly below the gate structure, wherein the entire counter-doping region is directly below the gate structure and the sidewall spacer, and wherein a dopant concentration of the counter-doping region is lower than a dopant concentration of the halo implant region, and the counter-doping region has a P-type impurity and a nitrogen ion.