Service-based architecture (SBA) has been introduced in the 5G core network design. It brings cloud-native features into core networks and shows implementation, deployment and service provision advantages. As cloud technologies have been penetrating radio access networks (RAN), it is beneficial to introduce service-oriented design into the last mile of mobile networks, offering a cloud-friendly end-to-end service-oriented architecture. Under such architecture, network functions are implemented as a service provider and service consumer that can be flexibly disaggregated and combined to offer different network implementations. This paper introduces 6G conceptual architecture based on service-oriented design principles. The architecture extends the service-oriented design into RAN. It allows network functions of RAN, core, and functions from applications to be integrated in a new way through service-based interfaces. The key elements of the architecture design are introduced. The paper identifies the important design aspects of 6G architecture and proposes a promising direction for the 6G architecture evolution.