# US 2014/0151686 A1 · Semiconductor device and method for manufacturing the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0151686 A1 - Document ID: US20140151686A1 - Status: Published application - Kind: A1 - Application number: 14/090,244 - Filed: 2013-11-26 - Published: 2014-06-05 - Earliest claimed: 2012-11-30 - Assignees: Semiconductor Energy Laboratory Co., Ltd. - Applicants: Semiconductor Energy Laboratory Co., Ltd. - Inventors: Shunpei YAMAZAKI; Yasutaka NAKAZAWA; Masami JINTYOU; Junichi KOEZUKA; Kenichi OKAZAKI; Takuya HIROHASHI; Shunsuke ADACHI - Web page: https://patentgrep.com/patent/US20140151686A1 ## CPC - H10D 30/6757: {characterised by the structure of the channel, e.g. transverse or longitudinal shape or doping profile (TFTs having channel structures for preventing kink or snapback effects H10D30/6708; TFTs having lightly-doped source or drain extensions H10D30/6715)} - H10D 30/6713: {characterised by the properties of the source or drain regions, e.g. compositions or sectional shapes} - H10D 30/6755: {Oxide semiconductors, e.g. zinc oxide, copper aluminium oxide or cadmium stannate} - H10D 86/423: {comprising semiconductor materials not belonging to the Group IV, e.g. InGaZnO} - H10D 86/60: wherein the TFTs are in active matrices - H10D 99/00: Subject matter not provided for in other groups of this subclass - H10P 14/412: {Deposition of metallic or metal-silicide materials} - H10P 14/692: composed of oxides, glassy oxides or oxide-based glasses - H10P 50/00: Etching of wafers, substrates or parts of devices - H10P 50/28: of insulating materials - H10K 59/1213: {the pixel elements being TFTs} - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES - H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10 - H10K: ORGANIC ELECTRIC SOLID-STATE DEVICES ## Abstract A semiconductor device including a transistor having a reduced number of oxygen vacancies in a channel formation region of an oxide semiconductor with stable electrical characteristics or high reliability is provided. A gate insulating film is formed over a gate electrode; an oxide semiconductor layer is formed over the gate insulating film; an oxide layer is formed over the oxide semiconductor layer by a sputtering method to form an stacked-layer oxide film including the oxide semiconductor layer and the oxide layer; the stacked-layer oxide film is processed into a predetermined shape; a conductive film containing Ti as a main component is formed over the stacked-layer oxide film; the conductive film is etched to form source and drain electrodes and a depression portion on a back channel side; and portions of the stacked-layer oxide film in contact with the source and drain electrodes are changed to an n-type by heat treatment. ## Claims ### Claim 1 A semiconductor device comprising: a gate electrode; a gate insulating film overlapping with the gate electrode; a stacked-layer oxide film including a channel formation region and overlapping with the gate electrode with the gate insulating film provided therebetween; and a source electrode and a drain electrode in contact with the stacked-layer oxide film, wherein portions of the stacked-layer oxide film which are in contact with the source electrode and the drain electrode have lowest resistance, and a portion of the stacked-layer oxide film has higher resistance as the portion is distanced from the source electrode or the drain electrode in a film thickness direction. ### Claim 2 (depends on 1) The semiconductor device according to claim 1, wherein an effective channel length is shorter than a distance between the source electrode and the drain electrode. ### Claim 3 (depends on 1) The semiconductor device according to claim 1, wherein the stacked-layer oxide film has a stacked-layer structure of a first oxide layer and a second oxide layer over the first oxide layer, and wherein the first oxide layer and the second oxide layer each contain In, Zn, and a metal other than In and Zn. ### Claim 4 (depends on 1) The semiconductor device according to claim 1, further comprising an oxide insulating film over the stacked-layer oxide film, the source electrode, and the drain electrode, wherein the oxide insulating film is in contact with a top surface of the stacked-layer oxide film between the source electrode and the drain electrode. ### Claim 5 (depends on 1) The semiconductor device according to claim 1, wherein the portions of the stacked-layer oxide film which are in contact with the source electrode and the drain electrode are n+ regions, and wherein the n+ regions are formed in such a manner that oxygen in the stacked-layer oxide film is extracted into the source electrode and the drain electrode. ### Claim 6 (depends on 1) The semiconductor device according to claim 1, wherein the portions of the stacked-layer oxide film which are in contact with the source electrode and the drain electrode are n+ regions, and wherein the n+ regions are extended in a region of the stacked-layer oxide film which is between the source electrode and the drain electrode. ### Claim 7 A semiconductor device comprising: a gate electrode; a gate insulating film overlapping with the gate electrode; a stacked-layer oxide film including a channel formation region and overlapping with the gate electrode with the gate insulating film provided therebetween; and a source electrode and a drain electrode in contact with the stacked-layer oxide film, wherein the stacked-layer oxide film includes a first oxide layer and a second oxide layer over the first oxide layer, wherein the second oxide layer comprises: a depression portion between the source electrode and the drain electrode; and low-resistance regions in portions in contact with the source electrode and the drain electrode and part of side surfaces of the depression portion, and wherein a depth of the depression portion is greater than a depth of the low-resistance regions in a film thickness direction. ### Claim 8 (depends on 7) The semiconductor device according to claim 7, wherein the low-resistance regions have lowest resistance, and a portion of the stacked-layer oxide film has higher resistance as the portion is distanced from the source electrode or the drain electrode in the film thickness direction. ### Claim 9 (depends on 7) The semiconductor device according to claim 7, wherein the first oxide layer and the second oxide layer each contain In, Zn, and a metal other than In and Zn. ### Claim 10 (depends on 7) The semiconductor device according to claim 7, further comprising an oxide insulating film over the stacked-layer oxide film, the source electrode, and the drain electrode, wherein the oxide insulating film is in contact with a top surface of the depression portion. ### Claim 11 (depends on 7) The semiconductor device according to claim 7, wherein the low-resistance regions are formed in such a manner that oxygen in the second oxide layer is extracted into the source electrode and the drain electrode. ### Claim 12 A method for manufacturing a semiconductor device comprising the steps of: forming a gate insulating film over a gate electrode; forming an oxide semiconductor layer over the gate insulating film; forming an oxide layer over the oxide semiconductor layer to form an stacked-layer oxide film containing the oxide semiconductor layer and the oxide layer; processing the stacked-layer oxide film into a predetermined shape; forming a conductive film containing Ti as a main component over and in contact with the stacked-layer oxide film; etching the conductive film to form a source electrode and a drain electrode, wherein a depression portion is formed in the oxide layer between the source electrode and the drain electrode; and performing a heat treatment, wherein low-resistance regions are formed in portions of the oxide layer which are in contact with the source electrode and the drain electrode, wherein a depth of the depression portion is greater than a depth of the low-resistance regions in a film thickness direction. ### Claim 13 (depends on 12) The method for manufacturing a semiconductor device according to claim 12, wherein the oxide semiconductor layer and the oxide layer are each an oxide containing In, M (Al, Ga, Y, La, Ce, or Nd), and Zn, and wherein the oxide layer has a proportion of M higher than the oxide semiconductor layer. ### Claim 14 (depends on 12) The method for manufacturing a semiconductor device according to claim 12, wherein the heat treatment is not performed between the step of processing the stacked-layer oxide film into the predetermined shape and the step of etching the conductive film. ### Claim 15 (depends on 12) The method for manufacturing a semiconductor device according to claim 12, wherein the low-resistance regions are formed in such a manner that oxygen in the oxide layer is extracted into the source electrode and the drain electrode. ### Claim 16 (depends on 12) The method for manufacturing a semiconductor device according to claim 12, wherein the conductive film is a stack of a first conductive layer containing Ti as a main component and a second conductive layer. ### Claim 17 (depends on 16) The method for manufacturing a semiconductor device according to claim 16, wherein the second conductive layer is any of a conductive layer containing Cu as a main component, a conductive layer containing Al as a main component, and a stack of a conductive layer containing Al as a main component and a conductive layer containing Ti as a main component. ### Claim 18 (depends on 12) The method for manufacturing a semiconductor device according to claim 12, wherein the low-resistance regions have lowest resistance, and a portion of the stacked-layer oxide film has higher resistance as the portion is distanced from the source electrode or the drain electrode in the film thickness direction ### Claim 19 (depends on 12) The method for manufacturing a semiconductor device according to claim 12, further comprising the step of forming an oxide insulating film over the stacked-layer oxide film, the source electrode, and the drain electrode, wherein the heat treatment is performed after the formation of the oxide insulating film. ### Claim 20 (depends on 19) The method for manufacturing a semiconductor device according to claim 19, wherein the oxide insulating film includes a first film configured to permeate oxygen and a second film containing oxygen at a proportion higher than a proportion of oxygen in the stoichiometric composition over the first film, and wherein the oxygen is released from the second film and moves to the stacked-layer oxide film through the first film by the heat treatment.