A method is provided for obtaining a semi-polar nitride layer obtained from a gallium and nitrogen based material on an upper surface of a crystalline substrate of cubic symmetry, including: etching parallel grooves from the upper surface having two opposed inclined facets, one having a crystalline orientation ; forming a mask above the upper surface such that the facets having orientation are not masked; and then forming the layer by epitaxial growth from the non-masked facets, including: a first epitaxial growth phase to form a seed in parallel grooves; interrupting the first phase when the seed has an inclined facet having a crystalline orientation 0001 and an upper facet having a crystalline semi-polar orientation 1011; a surface treatment step including modifying an upper portion of the seed to include silicon; and a second epitaxial growth phase from the inclined facet, continuing until coalescence of seeds of adjacent parallel grooves.