An actuating device for a friction clutch device installed in the drive train of a motor vehicle introduces actuating forces, especially clutch-engaging or clutch-releasing forces, to the friction clutch device to actuate at least one friction clutch of the friction clutch device in the engaging or releasing direction. More particularly, the claimed invention relates to a method of fabricating the semiconductor device in which parts of a gate electrode at the ends of a channel are lightly doped compared to the center part of the gate electrode, thereby eliminating a hump on a subthreshold current slope. Light intensity information about the measurement target in the thinning region is obtained, based on the interference signals for the respective wavelength sweeps, the interference signals remaining after thinning.