LaLuO₃ and LaScO₃ high-k layers were treated by flash lamp annealing (FLA) at temperatures between 1000 C and 1200 C for 3 or 20 ms. This procedure mimics the effect of an source/drain activation annealing by FLA on the electrical and microstructural properties of these alternative high-k dielectrics in a gate-first processing scheme. Related MOS capacitors with a TiN metal gate were processed in a gate-first like processing scheme. It is shown that 3 nm thick oxide layers resist crystallization even at 1200 C for 3 ms, while nanocrystallites are formed in thicker layers. The influence of the FLA treatment on capacitance-voltage (C-V) and current-voltage (I-V) characteristics are investigated. From these measurements, the effects on the relative dielectric constant (k), the fixed oxide charge density (Q_ox) as well as the leakage current through the insulators are deduced.