To provide a MOS transistor insensible to a temperature, and to provide a constant-voltage generator which is embodied from the MOS transistor insensible to a temperature and is stable to a temperature change without using a temperature compensating resistor.

In this MOS transistor, the number of source contacts is adjusted for increasing a source contact resistance, and the number of source contacts is smaller than the number of drain contacts. Further, for compensating for decreasing a current value between a desired source and drain by increasing the contact resistance of the source contact, the ratio of a width to the length of a gate is adjusted, and the ratio of a width is increased to the length of the gate.