Trust lies at the heart of a well-functioning and cohesive team. The members of the team should feel confident among each other that their peers' intentions are good. There is no reason to feel protective or careful around the group. Each and every teammate must feel comfortable being vulnerable and open to conflict.
The most important action the leader should take to encourage the building of trust within his team is to demonstrate first and foremost vulnerability himself through his own actions. This means that the leader will necessarily risk losing his own face in front of the team in order that the rest of the team will feel free to take similar risks themselves.
A true leader leads by example and creates an open and honest environment that fosters creativity and will never punish vulnerability.
See: The Five Dysfunctions of a Team