In this paper, an extended nested array strategy is proposed for degree of freedom (DOF) enhancement. Based on the augmented nested array (ANA), with the inter-element spacings in the side subarray increased, the strategy provides the possibility to acquire higher number of DOF than the existing nested-like arrays, such as the nested array, ANA, improved nested array and the maximum inter-element spacing constraint array. The one-side extended nested array (OS-ENA) is specifically proposed based on the ENA strategy, which can successfully avoid the holes brought by the sparse distribution of sensors and increase the DOF. The analytical expressions of sensor locations and DOF are derived. Simulations of the direction-of-arrival estimation verify the superiorities of the proposed OS-ENA with the spacial smoothing MUSIC algorithm used.