PURPOSE: A sensor circuit using a carbon nano tube is provided to improve sensitivity by using at least one transistor as a sensor. CONSTITUTION: An inverter(10) is comprised of a first transistor(M11) and a second transistor(M12). A carbon nano tube(CNT) is formed between a drain(D) and a source(S) of the first transistor. A carbon nano tube is formed between a drain and a source of the second transistor. At least one carbon nano tube of the first and second transistors is operated as a sensor. A switching element forms the same voltage in an input terminal and an output terminal before the sensor operates.
