EMR in 2 AZs and High Availability

No, currently Amazon EMR always launch all the nodes (master, core task) in a single AZ. With Instance fleet option you can specify multiple subnet while launching the cluster, however EMR will automatically pick one subnet (AZ) (based on best availability of nodes ).

With EMR multi master feature, EMR does launch 3 master nodes however they will be in same AZs only. Multi master feature is to reduce the probability of cluster termination due to master node termination. (which is a single point of failure in case of single master node cluster). In addition to that it does implement HA functionality for HDFS Namenode, Yarn Resource manager, Hbase master etc...