Defect generation in dielectrics under electrical stress is an important reliability issue for microelectronic devices. Most recent attention has focused on the generation of interface states and electron traps, while the creation of hole traps has rarely been reported. For example, there is hardly any information on the hole trap generation in oxynitrides and the generation under different temperatures has not been investigated. The objective of this work is to study the dependence of hole trap generation on temperature and nitridation. Based on new results, the role played by hydrogenous species in the generation is explored.