This paper studies the master-slave synchronization of delayed neural networks (DNNs), utilizing a sampled-data controller that incorporates communication delay. A semi-looped-functional approach is proposed, which results in a synchronization criterion with reduced conservatism. This criterion allows for the design of a sampled-data synchronization controller for DNNs that accommodates larger sampling intervals, thus reducing communication and computation burdens. The proposed approach incorporates more cross information of states and relaxes certain constraints of the overall functional, including the negative-definite constraints on its derivatives. Additionally, the proposed functional introduces states that fully consider the nonlinear characteristics of DNNs, along with delay and sampling information. Using these states, two zero-equations are constructed to reduce the conservativeness of the criterion. Two widely used numerical examples illustrate the effectiveness and superiority of the proposed criterion.