Microwave radiation may be applied to electrochemical devices for rapid thermal processing (RTP) (including annealing, crystallizing, densifying, forming, etc.) of individual layers of the electrochemical devices, as well as device stacks, including bulk and thin film batteries and thin film electrochromic devices. A method of manufacturing an electrochemical device may comprise: depositing a layer of the electrochemical device over a substrate; and microwave annealing the layer, wherein the microwave annealing includes selecting annealing conditions with preferential microwave energy absorption in the layer. An apparatus for forming an electrochemical device may comprise: a first system to deposit an electrochemical device layer over a substrate; and a second system to microwave anneal the layer, wherein the second system is configured to provide preferential microwave energy absorption in the device layer.