A semiconductor apparatus includes a detection voltage generation circuit configured to generate a first detection voltage and a second detection voltage of which voltage levels are varied according to characteristics of a PMOS transistor and an NMOS transistor in response to a detection enable signal, a code generation circuit configured to generate a detection code in response to the voltage levels of the first and second detection voltages, a reference voltage generation circuit configured to generate a reference voltage in response to the detection code, an internal voltage generation circuit configured to generate an internal voltage in response to the reference voltage, and an internal circuit configured to operate by receiving the internal voltage.