A transistor with superior electric characteristics is manufactured. An oxide insulating film is formed over a substrate, an oxide semiconductor film is formed over the oxide insulating film, heat treatment is then conducted at a temperature at which hydrogen contained in the oxide semiconductor film is desorbed and part of oxygen contained in the oxide insulating film is desorbed, then the heated oxide semiconductor film is etched into a predetermined shape to form an island-shaped oxide semiconductor film, a pair of electrodes is formed over the island-shaped oxide semiconductor film, a gate insulating film is formed over the pair of electrodes and the island-shaped oxide semiconductor film, and a gate electrode is formed over the gate insulating film.

A transistor with superior electric characteristics is manufactured. An oxide insulating film is formed over a substrate, an oxide semiconductor film is formed over the oxide insulating film, heat treatment is then conducted at a temperature at which hydrogen contained in the oxide semiconductor film is desorbed and part of oxygen contained in the oxide insulating film is desorbed, then the heated oxide semiconductor film is etched into a predetermined shape to form an island-shaped oxide semiconductor film, a pair of electrodes is formed over the island-shaped oxide semiconductor film, a gate insulating film is formed over the pair of electrodes and the island-shaped oxide semiconductor film, and a gate electrode is formed over the gate insulating film.

The present invention provides an etching liquid which has a suitable etching rate for etching of an oxide containing zinc and tin and is suppressed in change of the etching rate due to dissolution of the oxide, while being free from the generation of a precipitate. The corrosiveness of this etching liquid to wiring materials is low enough to be ignored, and this etching liquid has excellent linearity of a pattern shape. The present invention uses an etching liquid which contains (A) one or more substances selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid, methanesulfonic acid, perchloric acid and salts of these acids, and (B) oxalic acid or a salt thereof and water, and which has a pH of from −1 to 1.

The present invention provides an etching liquid which has a suitable etching rate for etching of an oxide containing zinc and tin and is suppressed in change of the etching rate due to dissolution of the oxide, while being free from the generation of a precipitate. The corrosiveness of this etching liquid to wiring materials is low enough to be ignored, and this etching liquid has excellent linearity of a pattern shape. The present invention uses an etching liquid which contains (A) one or more substances selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid, methanesulfonic acid, perchloric acid and salts of these acids, and (B) oxalic acid or a salt thereof and water, and which has a pH of from −1 to 1.

A Schottky source-gated thin film transistor is provided including: a drain contact; an insulating substrate; a source contact made of a Schottky metal; a channel connecting the buried source contact to the drain, the channel made of ZnO; and a Schottky source barrier formed between the source contact and the channel; and a gate; wherein the source contact is positioned below the channel.

A Schottky source-gated thin film transistor is provided including: a drain contact; an insulating substrate; a source contact made of a Schottky metal; a channel connecting the buried source contact to the drain, the channel made of ZnO; and a Schottky source barrier formed between the source contact and the channel; and a gate; wherein the source contact is positioned below the channel.

A method of metal-assisted chemical etching comprises forming an array of discrete metal features on a surface of a semiconductor structure, where each discrete metal feature comprises a porous metal body with a plurality of pores extending therethrough and terminating at the surface of the semiconductor structure. The semiconductor structure is exposed to an etchant, and the discrete metal features sink into the semiconductor structure as metal-covered surface regions are etched. Simultaneously, uncovered surface regions are extruded through the pores to form anchoring structures for the discrete metal features. The anchoring structures inhibit detouring or delamination of the discrete metal features during etching. During continued exposure to the etchant, the anchoring structures are gradually removed, leaving an array of holes in the semiconductor structure.

A method includes: in a semiconductor wafer having a first semiconductor layer and a second semiconductor layer adjoining the first semiconductor layer, forming a porous region extending from a front surface into the first semiconductor layer; and removing the porous region by an etching process, wherein a doping concentration of the second semiconductor layer is less than 10.sup.−2 times a doping concentration of the first semiconductor layer and/or a doping type of the second semiconductor layer is complementary to a doping type of the first semiconductor layer, wherein forming the porous region comprises bringing in contact a porosifying agent with the front surface of the first semiconductor layer and applying a voltage between the first semiconductor layer and a first electrode that is in contact with the porosifying agent, wherein applying the voltage comprises applying the voltage between the first electrode and an edge region of the first semiconductor layer.

A method includes: in a semiconductor wafer having a first semiconductor layer and a second semiconductor layer adjoining the first semiconductor layer, forming a porous region extending from a front surface into the first semiconductor layer; and removing the porous region by an etching process, wherein a doping concentration of the second semiconductor layer is less than 10.sup.−2 times a doping concentration of the first semiconductor layer and/or a doping type of the second semiconductor layer is complementary to a doping type of the first semiconductor layer, wherein forming the porous region comprises bringing in contact a porosifying agent with the front surface of the first semiconductor layer and applying a voltage between the first semiconductor layer and a first electrode that is in contact with the porosifying agent, wherein applying the voltage comprises applying the voltage between the first electrode and an edge region of the first semiconductor layer.

A method of processing a substrate includes: providing a substrate having one or more mandrels comprising a mandrel material, wherein a layer of a spacer material coats horizontal surfaces and sidewalls of the one or more mandrels; and etching and completely removing the layer of the spacer material from the horizontal surfaces of the one or more mandrels and thereby exposing the mandrel material, without completely removing the spacer material residing at the sidewalls of the one or more mandrels. The etching includes exposing the substrate to a plasma formed using a mixture comprising a first gas and a polymer-forming gas, and wherein the etching comprises forming a polymer on the substrate. Polymer-forming gas may include carbon (C) and hydrogen (H).