Abstract: There is provided a method for manufacturing a group-III nitride substrate, including: (a) preparing a substrate which is made of a group III-nitride crystal and which has a high oxygen concentration domain where an oxygen concentration is higher than that of a matrix of the crystal; (b) irradiating the substrate with laser beam aiming at the high oxygen concentration domain, forming a through-hole penetrating the substrate in a thickness direction, and removing at least a part of the high oxygen concentration domain from the substrate; and (c) embedding at least a part of an inside of the through-hole by growing the group-III nitride crystal in the through-hole.

Abstract: There is provided a method for manufacturing a nitride crystal substrate, including: arranging a plurality of seed crystal substrates made of a nitride crystal in a planar appearance, so that their main surfaces are parallel to each other and their lateral surfaces are in contact with each other; growing a first crystal film using a vapor-phase growth method on a surface of the plurality of seed crystal substrates arranged in the planar appearance, and preparing a combined substrate formed by combining the adjacent seed crystal substrates each other by the first crystal film; growing a second crystal film using a liquid-phase growth method on a main surface of the combined substrate so as to be embedded in a groove that exists at a combined part of the seed crystal substrates, and preparing a substrate for crystal growth having a smoothened main surface; and growing a third crystal film using the vapor-phase growth method, on the smoothed main surface of the substrate for crystal growth.

Abstract: A high voltage gallium nitride based semiconductor device includes an n-type gallium nitride freestanding substrate, and an n-type gallium nitride based semiconductor layer including a drift layer formed on the surface of the n-type gallium nitride freestanding substrate so as to have a reverse breakdown voltage of not less than 3000 V. The drift layer is configured such that a carbon concentration is not less than 3.0×1016/cm3 in a region which has an electric field intensity of not more than 1.5 MV/cm when a maximum allowable voltage where there occurs no breakdown phenomenon is applied as a reverse bias voltage.

Abstract: A manufacturing method of a piezoelectric film element includes forming a piezoelectric film including a lead-free alkali niobate based compound having a perovskite structure represented by a compositional formula of (K1-XNaX)NbO3 on a substrate, and dry-etching the piezoelectric film by using a low-pressure plasma including a fluorine system reactive gas.