Negative bias temperature instability (NBTI) lifetime prediction of thin gate insulator films based on hole injection without gate voltage acceleration is described and lifetime comparison between SiO2 film and SiON film is made based on the prediction method. The acceleration parameters are most important for the accurate lifetime prediction. The proposed acceleration parameter is not the applied voltage to the gate insulator film and the temperature but quantity of the hole injection to the gate insulator film that directly relates with the quantity of holes in the inversion layer. The degradation mechanism under the excessive voltage and excessive temperature stresses are different from that in the operation conditions. Using the hole injection method, the NBTI lifetime of SiON is less than that of SiO2. This result agrees with the reported results measured by conventional high gate fields and temperatures. By the introduction of effective stress time (=Qhole/Jinj0), accurate lifetime prediction in terms of the Vth shift is realized, and by analyzing of relationship between ID reduction and Vth shift, accurate lifetime prediction in terms of the ID reduction and the degradation prediction in the circuit level are realized. These results are essential for the accurate NBTI lifetime prediction for further more integrated LSI such as very thin gate insulator films around 1 nm.