According to one embodiment, a semiconductor device includes contact holes passing through a source region of a drain region of an interlayer insulating film and oxide semiconductor layer to reach an insulating substrate, wherein a source electrode and a drain electrode are formed inside the contact holes, respectively.

A semiconductor device (100A) includes a substrate (101) and a thin film transistor (10) supported by the substrate. The thin film transistor includes a gate electrode (102), an oxide semiconductor layer (104), a gate insulating layer (103), a source electrode (105) and a drain electrode (106). The oxide semiconductor layer includes an upper semiconductor layer (104b) which is in contact with the source electrode and the drain electrode and which has a first energy gap, and a lower semiconductor layer (104a) which is provided under the upper semiconductor layer and which has a second energy gap that is smaller than the first energy gap. The source electrode and the drain electrode include a lower layer electrode (105a, 106a) which is in contact with the oxide semiconductor layer and which does not contain Cu, and a major layer electrode (105b, 106b) which is provided over the lower layer electrode and which contains Cu. An edge of the lower layer electrode is at a position ahead of an edge of the major layer electrode.

A semiconductor device (100A) includes a substrate (101) and a thin film transistor (10) supported by the substrate. The thin film transistor includes a gate electrode (102), an oxide semiconductor layer (104), a gate insulating layer (103), a source electrode (105) and a drain electrode (106). The oxide semiconductor layer includes an upper semiconductor layer (104b) which is in contact with the source electrode and the drain electrode and which has a first energy gap, and a lower semiconductor layer (104a) which is provided under the upper semiconductor layer and which has a second energy gap that is smaller than the first energy gap. The source electrode and the drain electrode include a lower layer electrode (105a, 106a) which is in contact with the oxide semiconductor layer and which does not contain Cu, and a major layer electrode (105b, 106b) which is provided over the lower layer electrode and which contains Cu. An edge of the lower layer electrode is at a position ahead of an edge of the major layer electrode.

A method embodiment includes forming a patterned first photo resist over a seed layer. A first opening in the patterned first photo resist exposes the seed layer. The method further includes plating a first conductive material in the first opening on the seed layer, removing the patterned first photo resist, and after removing the patterned first photo resist, forming a patterned second photo resist over the first conductive material. A second opening in the patterned second photo resist exposes a portion of the first conductive material. The method further includes plating a second conductive material in the second opening on the first conductive material, removing the patterned second photo resist, and after removing the patterned second photo resist, depositing a dielectric layer around the first conductive material and the second conductive material.

Provided are an oxide semiconductor layer in which the number of defects is reduced and a highly reliable semiconductor device including the oxide semiconductor. A first oxide semiconductor layer having a crystal part is formed over a substrate by a sputtering method. A second oxide semiconductor layer is formed by a thermal chemical vapor deposition method over the first oxide semiconductor layer. The second oxide semiconductor layer is formed by epitaxial growth using the first oxide semiconductor layer as a seed crystal. A channel is formed in the second oxide semiconductor layer.

Provided are an oxide semiconductor layer in which the number of defects is reduced and a highly reliable semiconductor device including the oxide semiconductor. A first oxide semiconductor layer having a crystal part is formed over a substrate by a sputtering method. A second oxide semiconductor layer is formed by a thermal chemical vapor deposition method over the first oxide semiconductor layer. The second oxide semiconductor layer is formed by epitaxial growth using the first oxide semiconductor layer as a seed crystal. A channel is formed in the second oxide semiconductor layer.

A method for fabricating semiconductor device is disclosed. The method includes the steps of: providing a source layer; removing part of the source layer to form a first opening; forming a first channel layer in the first opening; forming a gate layer around the first channel layer and on the source layer; forming a drain layer on the gate layer and the first channel layer; removing part of the drain layer to form a second opening; and forming a second channel layer in the second opening.

A method for fabricating semiconductor device is disclosed. The method includes the steps of: providing a source layer; removing part of the source layer to form a first opening; forming a first channel layer in the first opening; forming a gate layer around the first channel layer and on the source layer; forming a drain layer on the gate layer and the first channel layer; removing part of the drain layer to form a second opening; and forming a second channel layer in the second opening.

A method of fabricating a semiconductor device includes applying a plasma to a portion of a metal dichalcogenide film. The metal dichalcogenide film includes a first metal and a chalcogen selected from the group consisting of S, Se, Te, and combinations thereof. A metal layer including a second metal is formed over the portion of the metal dichalcogenide film after applying the plasma.

A method of fabricating a semiconductor device includes applying a plasma to a portion of a metal dichalcogenide film. The metal dichalcogenide film includes a first metal and a chalcogen selected from the group consisting of S, Se, Te, and combinations thereof. A metal layer including a second metal is formed over the portion of the metal dichalcogenide film after applying the plasma.