Enterprise Engineering offers a global view on multiple concerns such as processes, stakeholders, supporting technology. This global view is sustained by Enterprise Architecture frameworks, languages, tools and standards. The current effort has been focused on general purpose Enterprise Architecture frameworks, modeling languages and tools, which allow describing a wide range of domains. While they are expressive enough at the business layer, at the technical layer, where more detail is needed to describe a domain specific system, such general purpose Enterprise Architecture Modeling Languages sometime lack the semantic strength required. The concepts present in the language are too abstract, they need refinement and specification. To provide the necessary specific semantic strength, this paper proposes an approach to extend Enterprise Architecture Modeling Languages with domain specificity. The proposed approach is a model-driven one, allowing a high degree of automation in the building of tools for the language extension. To better show its benefits, the approach is applied on the domain of Telecommunications, for defining an Enterprise Architecture Modeling Language extension for service creation. The so defined language and its associated tools are illustrated on an IP Multimedia Subsystem conferencing service example.