To attempt to improve the linearity and reproducibility by constituting a measuring circuit of a MOS transistor and constituting a sensor of a parasitic bipolar transistor or parasitic p-n junction diode formed from the element structure of a MOS transistor.

A p-channel MOS transistor P1 is formed in the p-type source/ drain diffused layer 104 on an n-type semiconductor substrate 101. An n-channel MOS transistor N1 is formed in the n-type source/drain region 103 on a p-type well region 102. A temperature sensor 1 is formed by using the region 102 and region 103, and a parasitic n-p-n bipolar transistor Q1 in which the substrate 101 is used as a collector, the region 102 is used as a base and the region 103 is used as an emitter is formed. The change amount of the voltage between the base and the emitter is detected as a temperature change amount. With the thus formed, the sensor which can be manufactured by a standard MOS process and has excellent linearity and reproducibility can be obtained.