 We describe a negative refraction effect for surface acoustic waves in two-dimensional phononic crystals made of cylindrical pillars assembled in a square lattice on a semi-infinite substrate, which occurs for the frequency range where the group velocity is never in opposite direction to the phase velocity. The use of cylindrical pillars acting as acoustic resonant elements on the surface allows us to achieve this phenomenon with a sub-wavelength feature size structure and design a flat lens for surface acoustic waves that focuses an acoustic source into an image on the other side of the finite size structure with an image resolution of lambda-4, which overcomes the Rayleigh diffraction limit. The numerical simulations are based on the efficient finite element method and analyze pillars and the substrate of lithium niobate. This article was authored by Mohammed A. Ulothor, Mammouda Douche, Abdelkrim Khalif, and others.