A semiconductor device includes an active layer having an active region, a source electrode, a drain electrode, a gate electrode, a source metal layer, a drain metal layer, and a source pad. The source metal layer and the drain metal layer are electrically connected to the source electrode and the drain electrode, respectively. An orthogonal projection of the drain metal layer on the active layer each forms a drain metal layer region. The source pad is electrically connected to the source metal layer. An orthogonal projection of the source pad on the active layer forms a source pad region overlapping the drain metal layer. An area of an overlapping region between the source pad region and the drain metal layer region is smaller than or equal to 40% of an area of the drain metal layer region.

The characteristic of Fe-doped HEMTs is improved. The invention provides a nitride semiconductor substrate having a substrate, a buffer layer made of nitride semiconductors on the substrate, and an active layer composed of nitride semiconductor layers on the buffer layer; the buffer layer containing Fe, the Fe having a concentration profile in which the Fe concentration increases monotonically and gradually in the thickness direction of the buffer layer from an interface between the substrate and the buffer layer, has a maximum value within 210.sup.17 to 1.110.sup.20 atoms/cm.sup.3 inclusive, and decreases monotonically and gradually toward an interface between the buffer layer and the active layer, and the point of the maximum value being within 50 nm from the midpoint in the thickness direction of the buffer layer, and being 500 nm or more away from the interface between the buffer layer and the active layer.

Methods for processing a semiconductor transistor are provided, where the semiconductor transistor includes a substrate, an epitaxial layer, and transistor components that are formed on the epitaxial layer. The method includes: removing a portion of the substrate that is disposed below a portion of the transistor components, to thereby expose a portion of a bottom surface of the epitaxial layer; forming an electrically insulating layer on the exposed portion of the bottom surface of the epitaxial layer; forming a via that extends from a bottom surface of the insulating layer to a bottom surface of one of the transistor components; depositing at least one metal layer on the bottom surface of the insulating layer, on a side wall of the via and on the bottom surface of one of the transistor components; and applying a solder paste to a bottom surface of the at least one metal layer.

A semiconductor device includes an active layer, a source electrode, a drain electrode, a gate electrode, a source pad, a drain pad, and a source external connecting element. The source electrode, the drain electrode, and the gate electrode are disposed on an active region of the active layer. The source pad is electrically connected to the source electrode and includes a body portion, a plurality of branch portions, and a current diffusion portion. The body portion is at least partially disposed on the active region of the active layer. The current diffusion portion interconnects the body portion and the branch portions. A width of the current diffusion portion is greater than a width of the branch portion and less than a half of a width of the body portion. The source external connecting element is disposed on the body portion and spaced from the current diffusion portion.

A semiconductor relay includes: a light-emitting element; and a light-receiving element facing the light-emitting element. The light-receiving element includes: a substrate; a semiconductor layer having a direct transition type, the semiconductor layer being disposed on the substrate and having a semi-insulating property; a first electrode having at least a part in contact with the semiconductor layer; and a second electrode having at least a part in contact with either one of the semiconductor layer and the substrate, in a position separated from the first electrode. The semiconductor layer is reduced in resistance by absorbing light from the light-emitting element.

A method for fabricating semiconductor device includes: forming a first semiconductor layer and an insulating layer on a substrate; removing the insulating layer and the first semiconductor layer to form openings; forming a second semiconductor layer in the openings; and patterning the second semiconductor layer, the insulating layer, and the first semiconductor layer to form fin-shaped structures.

Methods for processing a semiconductor transistor are provided, where the semiconductor transistor includes a substrate, an epitaxial layer, and transistor components that are formed on the epitaxial layer. The method includes: removing a portion of the substrate that is disposed below a portion of the transistor components, to thereby expose a portion of a bottom surface of the epitaxial layer; forming an electrically insulating layer on the exposed portion of the bottom surface of the epitaxial layer; forming a via that extends from a bottom surface of the insulating layer to a bottom surface of one of the transistor components; depositing at least one metal layer on the bottom surface of the insulating layer, on a side wall of the via and on the bottom surface of one of the transistor components; and applying a solder paste to a bottom surface of the at least one metal layer.

A field effect transistor includes: a semiconductor region including a first inactive region, an active region, and a second inactive region arranged side by side in a first direction; a gate electrode, a source electrode, and a drain electrode on the active region; a gate pad on the first inactive region; a gate guard on and in contact with the semiconductor region, the gate guard being apart from the gate pad and located between an edge on the first inactive region side of the semiconductor region and the gate pad; a drain pad on the second inactive region; a drain guard on and in contact with the semiconductor region, the drain guard being apart from the drain pad and located between an edge on the second inactive region side of the semiconductor region and the drain pad; and a metal film electrically connected to the gate guard.

There is provided a method for manufacturing a semiconductor device comprising: forming a first organic insulating layer on a semiconductor region; forming a bump base film including an edge portion contacting with the first organic insulating layer; performing heat treatment of the bump base film; and forming a second organic insulating layer so as to cover the edge portion of the bump base film and the first organic insulating layer around the bump base film while contacting with the first organic insulating layer, the second organic insulating layer being provided with a first opening that exposes a surface of the bump base film.

HEMT having a drain field plate is provided. The drain field plate is formed in the area between the gate and drain of a HEMT. The drain field plate includes a metal pad that has a larger projection area than the drain pad. The drain field plate and semiconductor layer disposed beneath the drain field plate form a metal-semiconductor (M-S) Schottky structure. The capacitance of the M-S Schottky structure generates capacitance in the semiconductor area, which increases the breakdown voltage of the transistor components of the HEMT. A portion of the substrate under the active area may be removed to thereby increase the heat conductivity and reduce the junction temperature of the transistor components of the HEMT.