A semiconductor device contrived to prevent a reference voltage and a reference current which are supplied to a high speed OCO from varying with a change in ambient temperature and/or a change in an external power supply voltage and to reduce the circuit area of a power supply module. The high speed OCO outputs a high speed clock whose magnitude is determined by the reference current and the reference voltage. A logic unit adjusts the values of the reference current and reference voltage, according to the reference voltage and reference current trimming codes related to detected ambient temperature and operating voltage.