Insulated gate bipolar transistor and method of making the same

A semiconductor device comprises a first base layer (1) for providing a PT-IGBT or IEGT structure, which includes a buffer layer (8) and a collector layer (9) provided in the buffer layer (8). A first activation rate, defined as the ratio of an activated first conductivity type impurity density ÄcmÜ in the buffer layer (8) measured by means of SR analysis to a first conductivity type impurity density ÄcmÜ in the buffer layer (8) measured by means of SIMS analysis is given by 25% or more, and a second activation rate, defined as the ratio of an activated second conductivity type impurity density ÄcmÜ in the collector layer (9) measured by means of SR analysis to a second conductivity type impurity density ÄcmÜ in the collector layer (9) measured by means of SIMS analysis is given by more than 0% and 10% or less.