A metal-insulator-metal (MIM) capacitor includes a semiconductor substrate and a capacitor device. The capacitor device includes a first conductor upright on the semiconductor substrate, a second conductor upright on the semiconductor substrate, and an insulator disposed used for insulating the first conductor from the second conductor. In a method for fabricating the capacitor device, a mask including a test line pattern and a capacitor pattern with a first trench pattern and a second trench pattern is used to form a test line and the first conductor and the second conductor of the capacitor device, thereby decreasing the cost of for fabricating the MIM capacitor.