Semiconductor device and method for fabricating the same

A semiconductor device comprising:

• a first MIS transistor formed in a first region of a semiconductor substrate;
• a second MIS transistor formed in a second region of the semiconductor substrate;
• and
• a third MIS transistor formed in a third region of the semiconductor substrate,
• wherein the first MIS transistor includes a first gate insulating film formed on the first region, a first gate electrode formed on the first gate insulating film, a first impurity doped layer formed in part of the first region located at each side of the first gate electrode and a first threshold control layer formed in part of the first region located under the first gate electrode,
• wherein the second MIS transistor includes a second gate insulating film formed on the second region, a second gate electrode formed on the second gate insulating film, a second impurity doped layer formed in part of the second region located at each side of the second gate electrode and a second threshold control layer formed in part of the second region located under the second gate electrode,
• wherein the third MIS transistor includes a third gate insulating film formed on the third region, a third gate electrode formed on the third gate insulating film, a third impurity doped layer formed in part of the third region located at each side of the third gate electrode and a third threshold control layer formed in part of the third region located under the third gate electrode,
• wherein a thickness of the second gate insulating film is substantially the same as or smaller than a thickness of the first gate insulating film and is larger than a thickness of the third gate insulating film,
• wherein the second impurity doped layer has substantially the same impurity concentration profile as an impurity concentration profile of the third impurity doped layer and has a lower impurity concentration than an impurity concentration of the first impurity doped layer, and
• wherein the second threshold control layer has substantially the same impurity concentration profile as an impurity concentration profile of the first threshold control layer and has a lower impurity concentration than an impurity concentration of the third threshold control layer.