A structure method for producing same provides suppressed lattice defects when epitaxially forming nitride layers over non-c-plane oriented layers, such as a semi-polar oriented template layer or substrate. A patterned mask with “window” openings, or trenches formed in the substrate with appropriate vertical dimensions, such as the product of the window width times the cotangent of the angle between the surface normal and the c-axis direction, provides significant blocking of all diagonally running defects during growth. In addition, inclined posts of appropriate height and spacing provide a blocking barrier to vertically running defects is created. When used in conjunction with the aforementioned aspects of mask windows or trenches, the post structure provides significant blocking of both vertically and diagonally running defects during growth.