In x Ga 1 − x As ( x = 0.06) layers were grown on patterned (1¯1¯1¯) GaAs substrates by liquid phase epitaxy. Two kinds of substrate structures were fabricated by using a GaAs wafer covered with aSiN x film. The first type was a substrate which had only regular windows of 1 mm in diameter in theSiN x film, and the second had trenches of 40–50 μm in depth in theSiN x windows. For trenchless substrates, InGaAs laterally extended on theSiN x film, finally resulted in a hexagonal shape. The etch pit density reduced dramatically on the epitaxial lateral overgrowth layer, but was extremely high on the substrate. For trench-type substrates, InGaAs layers grew laterally from the side wall of a trench towards the inside, forming a star-like pattern composed of {111}A and {111}B planes. Then, this pattern changed to a triangular shape surrounded by {111}B planes since the growth rate of {111}B planes was slower than that of {111}A planes. The InGaAs layer formed a bridge over the trench. As a result, the EPD was extremely low in both layers inside and outside except in the trench periphery. It was shown that the growth of high quality crystals was possible by using a trench-type substrate.