Patent ID: 7173447

Claim:
A method for diagnosing a fault in a semiconductor device, comprising: a laser applying step of applying a pulse laser beam having a predetermined wavelength to a semiconductor device so as to two-dimensionally scan the semiconductor device with the pulse laser beam, wherein a pulse width of the pulse laser beam is not shorter than 1 femtosecond, and is not longer than 10 picoseconds, and the semiconductor device is held at a state where no bias voltage is applied thereto; a detection/conversion step of detecting an electromagnetic wave generated by an optical beam induced current change produced at a laser applied position in the semiconductor device, and converting the detected electromagnetic wave into a time-varying voltage signal that corresponds to a time-varying amplitude of an electric field of the electromagnetic wave; and a fault diagnosis step of deriving an electric field distribution in the semiconductor device on the basis of the time-varying voltage signal to perform fault diagnosis on the semiconductor device.