Semiconductor device including ferroelectric tunnel barrier layer

Abstract

The invention relates to a semiconductor device including a ferroelectric tunnel barrier layer. A semiconductor device according to one aspect includes a first electrode layer, a ferroelectric tunnel barrier layer disposed over the first electrode layer, and a second electrode layer disposed over the ferroelectric tunnel barrier layer. The ferroelectric tunnel barrier layer includes oxygen vacancies. The second electrode layer includes a metal oxide. The second electrode layer has a relatively low conductive carrier density compared to the first electrode layer.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to Korean Application No. 10 - 2023 - 0187251, filed with the Korean Intellectual Property Office on December 20, 2023, which is incorporated herein by reference in its entirety. Technical field

[0003] The present disclosure generally relates to semiconductor devices including a ferroelectric tunnel barrier layer. Background art

[0004] A ferroelectric material is a material that has spontaneous polarization in a state where no external electric field is applied. The spontaneous polarization can be realized as, for example, a pair of remanent polarization states with different orientations. This pair of remanent polarization states can be switched by applying an external electric field. The polarization characteristics of the ferroelectric material can be used to store signal information of "0" and "1" in a non - volatile manner.

[0005] As an example, research is being conducted on ferroelectric materials as the dielectric layer of a unit capacitor. As another example, research is being conducted on using a ferroelectric material as the gate dielectric layer of a transistor (as a storage element in the structure). Additionally, research is being conducted on using a ferroelectric tunnel barrier layer as a storage element in a tunnel barrier device, where the ferroelectric tunnel barrier layer is disposed between a pair of electrodes. Summary of the invention

[0006] A semiconductor device according to an embodiment of the present disclosure may include: a first electrode layer, a ferroelectric tunnel barrier layer disposed on the first electrode layer, and a second electrode layer disposed on the ferroelectric tunnel barrier layer. The ferroelectric tunnel barrier layer includes oxygen vacancies. The second electrode layer includes a metal oxide. The second electrode layer has a relatively low conductive carrier density compared to the first electrode layer.

[0007] A semiconductor device according to another embodiment of the present disclosure may include: a first electrode layer, a ferroelectric tunnel barrier layer disposed on the first electrode layer, an oxygen storage layer disposed on the ferroelectric tunnel barrier layer, and a second electrode layer disposed on the oxygen storage layer.

[0008] A semiconductor device according to another embodiment of the present disclosure may include: a first electrode layer, a ferroelectric tunnel barrier layer disposed on the first electrode layer, and a second electrode layer including a metal oxide disposed on the ferroelectric tunnel barrier layer. The ferroelectric tunnel barrier layer may include: a first ferroelectric portion including a first concentration of oxygen vacancies; and a second ferroelectric portion including a second concentration of oxygen vacancies higher than the first concentration. Brief description of the drawings

[0009] Figure 1is a cross-sectional view schematically showing a semiconductor device according to an embodiment of the present disclosure.

[0010] Figure 2 and Figure 3 is a diagram schematically showing the operation of a semiconductor device according to an embodiment of the present disclosure.

[0011] Figure 4 is a cross-sectional view schematically showing a semiconductor device according to another embodiment of the present disclosure.

[0012] Figure 5 and Figure 6 is a diagram schematically showing the operation of a semiconductor device according to another embodiment of the present disclosure.

[0013] Figure 7 is a cross-sectional view schematically showing a semiconductor device according to still another embodiment of the present disclosure.

[0014] Figure 8 and Figure 9 is a diagram schematically showing the operation of a semiconductor device according to an embodiment of the present disclosure.

[0015] Figure 10 is a cross-sectional view schematically showing a semiconductor device according to still another embodiment of the present disclosure.

[0016] Figure 11 is a cross-sectional view schematically showing a semiconductor device according to still another embodiment of the present disclosure.

[0017] Figure 12 is a cross-sectional view schematically showing a semiconductor device according to still another embodiment of the present disclosure. Detailed Description

[0018] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, the dimensions of the components (e.g., the width and thickness of the components) are enlarged to clearly show each component of the device. The terms used herein may correspond to words selected in consideration of their functions in the embodiments, and the meanings of the terms may be interpreted differently by those of ordinary skill in the art to which the embodiments belong. If clearly defined in detail, the terms may be interpreted according to the definition. Unless otherwise defined, the terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the embodiments belong. In addition, unless clearly stated otherwise in the context, the expression of the singular form of a word should be understood to include the plural form of the word.

[0019] In this specification, a write operation of a semiconductor device may refer to an operation of applying a write voltage to a ferroelectric tunnel barrier layer to form a remanent polarization having a predetermined orientation in the ferroelectric tunnel barrier layer and simultaneously generating or removing a conductive protrusion in the ferroelectric tunnel barrier layer. The remanent polarization may be non-volatilely stored as signal information in the ferroelectric tunnel barrier layer. Additionally, in this specification, a read operation of a semiconductor device may refer to an operation of applying a read voltage at a level that does not change the orientation of the remanent polarization stored in the ferroelectric tunnel barrier layer and measuring a tunneling current passing through the ferroelectric tunnel barrier layer. Based on the measured tunneling current, the signal information stored in the ferroelectric tunnel barrier layer may be read. That is, a semiconductor device according to an embodiment of the present disclosure may be a ferroelectric tunnel barrier device.

[0020] In this specification, an "on state" may refer to a conductive state presented by the ferroelectric tunnel barrier layer of a semiconductor device. The conductive state may be caused by a rapid increase in the tunneling current passing through the ferroelectric tunnel barrier layer. In contrast, an "off state" may refer to an electrically insulating state presented by the ferroelectric tunnel barrier layer of a semiconductor device. In the electrically insulating state, the tunneling current passing through the ferroelectric tunnel barrier layer may be reduced or suppressed.

[0021] Figure 1 is a cross-sectional view schematically showing a semiconductor device according to an embodiment of the present disclosure. Referring to Figure 1 , the semiconductor device 1 may include a first electrode layer 110, a ferroelectric tunnel barrier layer 120 disposed on the first electrode layer 110, and a second electrode layer 130 disposed on the ferroelectric tunnel barrier layer 120.

[0022] The first electrode layer 110 may include a conductive material. In an embodiment, the first electrode layer 110 may include an inert metal. As a non-limiting example, the inert metal may include gold (Au), platinum (Pt), ruthenium (Ru), iridium (Ir), etc.

[0023] The ferroelectric tunnel barrier layer 120 may include a ferroelectric material having a remanent polarization. The ferroelectric material may include, for example, hafnium oxide, zirconium oxide, hafnium zirconium oxide, or a combination of two or more thereof. Additionally, the ferroelectric tunnel barrier layer 120 may have a thickness of, for example, about 1 nanometer (nm) to about 20 nm. The ferroelectric tunnel barrier layer 120 may include oxygen vacancies that may move by an electric field applied to the ferroelectric tunnel barrier layer 120, as described with reference to Figure 2 and Figure 3 .

[0024] The ferroelectric tunnel barrier layer 120 may have a pair of remanent polarization states having different polarization orientations. According to the orientation of the remanent polarization, the characteristics of the tunneling current passing through the ferroelectric tunnel barrier layer 120 may change.

[0025] The second electrode layer 130 may include a conductive metal oxide. For example, the conductive metal oxide may include ruthenium oxide (RuO2), iridium oxide (IrO2), platinum oxide (PtO2), strontium ruthenate (SrRuO3), a metal perovskite oxide, a conductive pyrochlore oxide, or a combination of two or more thereof. The metal perovskite oxide may include, for example, niobium-doped strontium titanate (Nb-doped SrTiO3). The conductive pyrochlore oxide may include, for example, lead iridium oxide (Pb2Ir2O7) or bismuth ruthenium oxide (Bi2Ru2O7).

[0026] Compared with the first electrode layer 110, the second electrode layer 130 may have a relatively low electron density as conductive carriers. In addition, in a region adjacent to the ferroelectric tunnel barrier layer 120, the density of conductive electrons in the second electrode layer 130 may be affected by the remanent polarization of the ferroelectric tunnel barrier layer 120. Therefore, as will be described later with reference to Figure 2 and Figure 3 Due to the remanent polarization of the ferroelectric tunnel barrier layer 120, an electron accumulation region 111 or an electron depletion region 112 may be formed in an internal region of the second electrode layer 130 adjacent to the interface between the ferroelectric tunnel barrier layer 120 and the second electrode layer 130.

[0027] In an embodiment, the second electrode layer 130 may supply oxygen ions to the ferroelectric tunnel barrier layer 120. As will be described later with reference to Figure 2 In response to oxygen ions moving into the ferroelectric tunnel barrier layer 120 under the action of an external voltage, oxygen vacancies may accumulate in the ferroelectric tunnel barrier layer 120 to generate a conductive protrusion ( Figure 2 F120 in).

[0028] As described above, a semiconductor device according to an embodiment of the present disclosure may include a ferroelectric tunnel barrier layer disposed between a first electrode layer and a second electrode layer. The ferroelectric tunnel barrier layer may include a ferroelectric material. A conductive protrusion of oxygen vacancies may be generated or removed from the ferroelectric tunnel barrier layer.

[0029] Figure 2 and Figure 3 are diagrams schematically showing the operation of a semiconductor device according to an embodiment of the present disclosure. A method of operating a semiconductor device may be described using Figure 1 the semiconductor device 1 of. Specifically, Figure 2 is a diagram showing a first write operation in which the state of the semiconductor device 1 is converted to an electrically conductive state. Figure 2 The internal structure and energy band diagram of the semiconductor device 1 after the completion of the first write operation may be schematically shown. Figure 3 is a diagram showing a second write operation in which the state of the semiconductor device 1 is converted to an electrically off state. Figure 3The internal structure and energy band diagram of the semiconductor device 1 can be schematically shown after the second writing operation is completed.

[0030] Referring to Figure 2 , during the first writing operation of the semiconductor device 1, a predetermined first writing voltage can be applied between the first electrode layer 110 and the second electrode layer 130. The first writing voltage can have a level sufficient to switch the polarization orientation of the ferroelectric material within the ferroelectric tunnel barrier layer 120. The first writing voltage can be a voltage configured such that the bias applied to the second electrode layer 130 has a negative polarity while the bias applied to the first electrode layer 110 has a positive polarity.

[0031] Referring to Figure 2 , by applying the first writing voltage, a polarization with a first polarization orientation P1 can be formed in the ferroelectric tunnel barrier layer 120. The electric field generated by the polarization can induce electrons into the internal region of the second electrode layer 130 adjacent to the interface between the ferroelectric tunnel barrier layer 120 and the second electrode layer 130 to form an electron accumulation region 111. In the electron accumulation region 111, the conduction band energy level Ec-130 of the second electrode layer 130 can be lower than the Fermi energy level Ef-130 of the second electrode layer 130. Therefore, the second electrode layer 130 in the electron accumulation region 111 can generate a sufficient electron density for tunneling. On the other hand, since the first electrode layer 110 has a higher electron density than the second electrode layer 130, the internal region of the first electrode layer 110 adjacent to the interface with the ferroelectric tunnel barrier layer 120 can be relatively less affected by the electric field generated by the polarization. Therefore, an electron defect region may not be formed in the region of the first electrode layer 110 adjacent to the ferroelectric tunnel barrier layer 120. That is, the energy band diagram does not change in the region of the first electrode layer 110 adjacent to the ferroelectric tunnel barrier layer 120.

[0032] Referring to Figure 2, when a first write voltage is applied between the first electrode layer 110 and the second electrode layer 130, positively charged vacancies can accumulate in the ferroelectric tunnel barrier layer 120 to form a conductive protrusion F120. The conductive protrusion F120 can extend from the interface between the second electrode layer 130 inside the ferroelectric tunnel barrier layer 120 and the ferroelectric tunnel barrier layer 120 towards the first electrode layer 110. According to one of various assumptions, oxygen ions inside the second electrode layer 130 can be supplied to the ferroelectric tunnel barrier layer 120 by the first write voltage, and oxygen vacancies inside the ferroelectric tunnel barrier layer 120 can move towards the second electrode layer 130 in a direction opposite to the conduction direction of the oxygen ions. After the oxygen vacancies accumulate at the interface between the second electrode layer 130 and the ferroelectric tunnel barrier layer 120, the oxygen vacancies can grow inside the ferroelectric tunnel barrier layer 120 to generate the conductive protrusion F120. According to another assumption, due to the bias of the negative polarity (i.e., the first write voltage) applied to the second electrode layer 130, oxygen vacancies distributed within the ferroelectric tunnel barrier layer 120 can move towards the second electrode layer 130. The oxygen vacancies moved to the second electrode layer 130 via electrostatic attraction can accumulate at the interface between the second electrode layer 130 and the ferroelectric tunnel barrier layer 120, and then can grow inside the ferroelectric tunnel barrier layer 120 to generate the conductive protrusion F120.

[0033] According to an embodiment of the present disclosure, the growth of the conductive protrusion F120 can be controlled such that the conductive protrusion F120 does not reach the first electrode layer 110. That is, the conductive protrusion F120 can maintain a non-contact state with the first electrode layer 110. The conductive protrusion F120 can be formed to be spaced apart from the first electrode layer 110. The growth of the conductive protrusion F120 can be controlled by controlling the application of the first write voltage. As an example, the first write voltage can be applied in the form of a pulsed voltage, and the growth of the conductive protrusion F120 can be controlled by controlling the number of times the pulsed voltage is applied. The conductive protrusion F120 can include oxygen vacancies having positive charges such that the conductive protrusion F120 can serve as a conduction path for conductive carriers (e.g., electrons).

[0034] After forming the electron accumulation region 111 and the conductive protrusion F120 by the controlled application of the first write voltage, the first write operation can be completed by removing the first write voltage. After removing the first write voltage, a first residual polarization state having a first polarization orientation P1 can be maintained in the ferroelectric tunnel barrier layer 120. Accordingly, the electron accumulation region 111 can be maintained in the second electrode layer 130. Additionally, after removing the first write voltage, the conductive protrusion F120 can be maintained within the ferroelectric tunnel barrier layer 120. Due to the conductive protrusion F120, the tunneling width of electrons tunneling for conduction can be reduced from a first width W1 corresponding to the thickness of the ferroelectric tunnel barrier layer 120 to a first tunneling width W-f1. In Figure 2 andFigure 3 In this case, the conduction band energy level of the ferroelectric tunnel barrier layer 120 is labeled as Ec-120, while the Fermi energy level of the first electrode layer 110 is labeled as Ef-110.

[0035] As described above, by performing the first writing operation, the first remaining polarization state of the first polarization orientation P1 can be stored as the first signal information in the ferroelectric tunnel barrier layer 120. At the same time, the conductive protrusion F120 can be formed to extend from the interface between the ferroelectric tunnel barrier layer 120 and the second electrode layer 130 toward the first electrode layer 110 and into the interior of the ferroelectric tunnel barrier layer 120. The conductive protrusion F120 does not contact the first electrode layer 110.

[0036] Thereafter, when performing the reading operation, a reading voltage that does not switch the level of the first remaining polarization state can be applied between the first electrode layer 110 and the second electrode layer 130. The reading voltage can have the same polarity as the first writing voltage. When the reading voltage is applied, tunneling may occur through the electrons formed in the electron accumulation region 111, thereby converting the state of the semiconductor device ( Figure 1 of 1) to the on state. The conductive protrusion F120 can reduce the tunneling width of the electrons, thereby increasing the tunneling efficiency of the electrons and increasing the tunneling current density. As described below with reference to Figure 3 In the off state, the conductive protrusion F120 can be completely or partially removed, and the tunneling current density can be reduced. Therefore, the conductive protrusion F120 can increase the switching ratio of the semiconductor device 1.

[0037] Referring to Figure 3 , a predetermined second writing voltage can be applied between the first electrode layer 110 and the second electrode layer 130 to perform the second writing operation of the semiconductor device 1. The second writing voltage can have a level sufficient to switch the orientation of the first remaining polarization state stored in the ferroelectric tunnel barrier layer 120. The second writing voltage can be a voltage configured such that the bias applied to the second electrode layer 130 has a positive polarity and the bias applied to the first electrode layer 110 has a negative polarity.

[0038] Referring to Figure 3, by applying a second write voltage, a polarization with a second polarization orientation P2 can be formed in the ferroelectric tunnel barrier layer 120. The electric field generated by the polarization can form an electron-deficient region 112 in the internal region of the second electrode layer 130 adjacent to the interface between the ferroelectric tunnel barrier layer 120 and the second electrode layer 130. When the second write operation is performed, the electron accumulation region 111 formed by the first write operation can be converted into the electron-deficient region 112. In the electron-deficient region 112, the conduction band energy level Ec-130 of the second electrode layer 130 can be higher than the Fermi energy level Ef-130. Therefore, the electron-deficient region 112 of the second electrode layer 130 cannot provide sufficient electron density for tunneling.

[0039] On the other hand, since the first electrode layer 110 has a higher electron density than the second electrode layer 130, the region of the first electrode layer 110 adjacent to the interface with the ferroelectric tunnel barrier layer 120 can be relatively less affected by the electric field generated by the polarization. Therefore, in the region of the first electrode layer 110 adjacent to the ferroelectric tunnel barrier layer 120, an electron accumulation region may not be formed. That is, in the region of the first electrode layer 110 adjacent to the ferroelectric tunnel barrier layer 120, the energy band diagram may not change.

[0040] Referring to Figure 3 , when a second write voltage is applied between the first electrode layer 110 and the second electrode layer 130, the conductive protrusion F120 formed in the ferroelectric tunnel barrier layer 120 can be removed or dissipated. When the oxygen vacancies constituting the protrusion diffuse into the ferroelectric tunnel barrier layer 120, the conductive protrusion F120 can be decomposed under the second write voltage. Although Figure 3 shows that the conductive protrusion F120 is completely removed by the second write voltage, the present disclosure is not necessarily limited thereto. In some embodiments, the conductive protrusion F120 can be partially removed. Under the second write voltage, the length of the remaining conductive protrusion F120 in the layer thickness direction can be shorter than Figure 2 the length of the conductive protrusion F120 of

[0041] After forming the electron-deficient region 112 by applying the second write voltage and completely or partially removing the conductive protrusion F120, the second write operation can be completed by removing the second write voltage. After removing the second write voltage, a second remaining polarization state with the second polarization orientation P2 can be maintained in the ferroelectric tunnel barrier layer 120. Therefore, the electron-deficient region 112 can be maintained within the second electrode layer 130. In addition, even after removing the second write voltage, the conductive protrusion F120 can remain completely or partially removed. When the electron-deficient region 112 is formed, the tunneling width through which electrons must tunnel for conduction can increase from a first width W1 corresponding to the thickness of the ferroelectric tunnel barrier layer 120 to a second tunneling width W-r1.

[0042] As described above, by performing the second writing operation, the second remaining polarization state of the second polarization orientation P2 can be stored as second signal information in the ferroelectric tunnel barrier layer 120. At the same time, the conductive protrusion F120 extending from the interface between the ferroelectric tunnel barrier layer 120 and the second electrode layer 130 into the ferroelectric tunnel barrier layer 120 can be completely or partially removed.

[0043] Thereafter, when a read operation is performed by a read voltage, the tunneling current can be reduced and suppressed, thereby presenting an off state.

[0044] In an embodiment of the present disclosure, in the off state, the conductive protrusion F120 in the on state can be completely or partially removed, so that the density of the tunneling current can be reduced relatively greatly. As a result, according to an embodiment of the present disclosure, the on / off ratio of the semiconductor device can be increased by controlling the generation and removal of the conductive protrusion F120 in the ferroelectric tunnel barrier layer 120.

[0045] Figure 4 is a cross-sectional view schematically showing a semiconductor device according to another embodiment of the present disclosure. Referring to Figure 4 , compared with the semiconductor device 1 described with reference to Figure 1 , the semiconductor device 2 may further include a protrusion control layer 224 arranged as a part of the ferroelectric tunnel barrier layer 220.

[0046] The semiconductor device 2 may include a first electrode layer 210, a ferroelectric tunnel barrier layer 220 disposed on the first electrode layer 210, and a second electrode layer 230 disposed on the ferroelectric tunnel barrier layer 220. The first electrode layer 210 and the second electrode layer 230 may be substantially the same as the first electrode layer 110 and the second electrode layer 130 of the semiconductor device 1 described above with reference to Figure 1 . In an embodiment, the first electrode layer 210 may include an inert metal, and the second electrode layer 230 may include a conductive metal oxide.

[0047] The ferroelectric tunnel barrier layer 220 may include a first ferroelectric layer 222a, a protrusion control layer 224, and a second ferroelectric layer 222b sequentially disposed on the first electrode layer 210. The material of each of the first ferroelectric layer 222a and the second ferroelectric layer 222b may be substantially the same as the material of the ferroelectric tunnel barrier layer 120 of the semiconductor device 1 described above with reference to Figure 1 . In an embodiment, the first ferroelectric layer 222a and the second ferroelectric layer 222b may be formed of substantially the same material. That is, each of the first ferroelectric layer 222a and the second ferroelectric layer 222b may include, for example, hafnium oxide, zirconium oxide, hafnium zirconium oxide, or a combination of two or more thereof. As an example, the sum of the thicknesses of the first ferroelectric layer 222a and the second ferroelectric layer 222b may be about 1 nm to about 20 nm.

[0048] Referring to Figure 4 , the protrusion control layer 224 can be disposed on the first ferroelectric layer 222a and can be used to prevent the growth of the conductive protrusion F220, as will be described later with reference to Figure 5 . For example, the protrusion control layer 224 can include amorphous silicon oxide or amorphous aluminum oxide. The second ferroelectric layer 222b can be disposed on the protrusion control layer 224. The thickness of the protrusion control layer 224 can be less than the thickness of each of the first ferroelectric layer 222a and the second ferroelectric layer 222b.

[0049] In an embodiment, the distance d2 from the second electrode layer 230 to the protrusion control layer 224 can be 1 / 4 to 1 / 2 of the distance d1 between the first electrode layer 210 and the second electrode layer 230. In this case, the thickness of the second ferroelectric layer 222b can be less than the thickness of the first ferroelectric layer 222a.

[0050] Figure 5 and Figure 6 are diagrams schematically showing the operation of a semiconductor device according to an embodiment of the present disclosure. A method of operating a semiconductor device can be described using the Figure 4 semiconductor device 2. Specifically, Figure 5 is a diagram showing a first write operation for converting the state of the semiconductor device 2 into an electrically conductive state. Figure 5 The internal structure and energy band diagram of the semiconductor device 2 after the completion of the first write operation can be schematically shown. Figure 6 is a diagram showing a second write operation for converting the state of the semiconductor device 2 into an electrically off state. Figure 6 The internal structure and energy band diagram of the semiconductor device 2 after the completion of the second write operation can be schematically shown.

[0051] Referring to Figure 5 , the first write operation of the semiconductor device 2 can be performed by applying a predetermined first write voltage. The first write voltage can be a voltage configured such that the bias applied to the second electrode layer 230 has a negative polarity and the bias applied to the first electrode layer 210 has a positive polarity.

[0052] By applying the first write voltage, a polarization having a first polarization orientation P1 can be formed in the ferroelectric tunnel barrier layer 220. The electric field generated by the polarization can induce electrons into the internal region of the second electrode layer 230 adjacent to the interface between the ferroelectric tunnel barrier layer 220 and the second electrode layer 230 to form an electron accumulation region 211.

[0053] In addition, when a first write voltage is applied between the first electrode layer 210 and the second electrode layer 230, positively charged oxygen vacancies can accumulate in the ferroelectric tunnel barrier layer 220 to form a conductive protrusion F220. Specifically, when the first write voltage is applied, the conductive protrusion F220 can grow from the interface between the second electrode layer 230 and the second ferroelectric layer 222b and extend into the interior of the second ferroelectric layer 222b toward the protrusion control layer 224. The growth of the conductive protrusion F220 can stop after the conductive protrusion F220 reaches the protrusion control layer 224.

[0054] As a result, the growth of the conductive protrusion F220 can be effectively controlled. The protrusion control layer 224 can be used as a barrier layer to prevent the conductive protrusion F220 from growing into the first ferroelectric layer 222a. Therefore, the growth of the conductive protrusion F220 can be restricted and confined within the second ferroelectric layer 222b of the ferroelectric tunnel barrier layer 220.

[0055] In one embodiment, since the distance d2 from the second electrode layer 230 to the protrusion control layer 224 is 1 / 4 to 1 / 2 of the distance d1 between the first electrode layer 210 and the second electrode layer 230, the length of the conductive protrusion F220 along the thickness direction of the ferroelectric tunnel barrier layer 220 can be 1 / 4 to 1 / 2 of the distance d1 between the first electrode layer 210 and the second electrode layer 230.

[0056] Figure 5 In, the shapes of the Fermi level Ef-230 and the conduction band level Ec-230 of the second electrode layer 230, the shape of the conduction band level Ec-220 of the ferroelectric tunnel junction layer 220, and the shape of the Fermi level Ef-210 of the first electrode layer 210 are the same as those of Figure 2 shown in the Fermi level Ef-130 and the conduction band level Ec-130 of the second electrode layer 130, the shape of the conduction band level Ec-120 of the ferroelectric tunnel junction layer 120, and the shape of the Fermi level Ef-110 of the first electrode layer 110. Due to the conductive protrusion F220, the tunneling width of the electrons tunneling for conduction can be reduced from a first width W2 corresponding to the thickness of the ferroelectric tunnel barrier layer 220 to a first tunneling width W-f2.

[0057] Referring to Figure 6 , a predetermined second write voltage can be applied between the first electrode layer 210 and the second electrode layer 230 to perform a second write operation of the semiconductor device 2. The second write voltage can be a voltage configured such that the bias applied to the second electrode layer 230 has a positive polarity and the bias applied to the first electrode layer 210 has a negative polarity.

[0058] Referring to Figure 6, by applying a second write voltage, a polarization having a second polarization orientation P2 can be formed in the ferroelectric tunnel barrier layer 220. The electric field generated by the polarization can form an electron-deficient region 212 in an internal region of the second electrode layer 230 adjacent to the interface between the ferroelectric tunnel barrier layer 220 and the second electrode layer 230.

[0059] In addition, when a second write voltage is applied between the first electrode layer 210 and the second electrode layer 230, the conductive protrusion F220 formed in the second ferroelectric layer 222b can be removed or can dissipate. When the oxygen vacancies constituting the conductive protrusion F220 are discharged into the second ferroelectric layer 222b under the second write voltage, the conductive protrusion F220 can decompose. Although Figure 6 it is shown that the conductive protrusion F220 is completely removed by the second write voltage, the present disclosure is not necessarily limited thereto. In some embodiments, the conductive protrusion F220 can be partially removed. When the conductive protrusion F220 dissipates or is partially removed, the length of the remaining conductive protrusion F220 in the layer thickness direction can be shorter than Figure 5 the length of the conductive protrusion F220. In Figure 6 , the shapes of the Fermi level Ef-230 and the conduction band level Ec-230 of the second electrode layer 230, the shape of the conduction band level Ec-220 of the ferroelectric tunnel junction layer 220, and the shape of the Fermi level Ef-210 of the first electrode layer 210 are substantially the same as the shapes of the Fermi level Ef-130 and the conduction band level Ec-130 of the second electrode layer 130, the shape of the conduction band level Ec-120 of the ferroelectric tunnel junction layer 120, and the shape of the Fermi level Ef-110 of the first electrode layer 110 as shown in Figure 3 . When the electron-deficient region 212 is formed, the tunneling width through which electrons must tunnel to conduct electricity can increase from a first width W2 corresponding to the thickness of the ferroelectric tunnel barrier layer 120 to a second tunneling width W-r2.

[0060] As described above, according to an embodiment of the present disclosure, when the first write operation and the second write operation are performed, the position of the conductive protrusion F220 can be limited to the second ferroelectric layer 222b of the ferroelectric tunnel barrier layer 220. Therefore, the reliability of the switching operation of the semiconductor device 2 can be improved.

[0061] Figure 7 is a cross-sectional view schematically showing a semiconductor device according to another embodiment of the present disclosure. Referring to Figure 7 , compared with the semiconductor device 1 described with reference to Figure 1 , the semiconductor device 3 can have a ferroelectric tunnel barrier layer with a different structure.

[0062] The semiconductor device 3 may include a first electrode layer 310, a ferroelectric tunnel barrier layer 320 disposed on the first electrode layer 310, and a second electrode layer 330 disposed on the ferroelectric tunnel barrier layer 320. The first electrode layer 310 and the second electrode layer 330 may be substantially the same as the first electrode layer 110 and the second electrode layer 120 of the semiconductor device 1 described above with reference to Figure 1 . In an embodiment, the first electrode layer 310 may include an inert metal, and the second electrode layer 330 may include a conductive metal oxide.

[0063] The ferroelectric tunnel barrier layer 320 may include a first ferroelectric portion 322 and a second ferroelectric portion 324 sequentially disposed on the first electrode layer 310. The first ferroelectric portion 322 may include a first concentration of oxygen vacancies. The second ferroelectric portion 324 may include a second concentration of oxygen vacancies that is higher than the first concentration. As Figure 7 shown, the second ferroelectric portion 324 may be disposed closer to the second electrode layer 330 than the first ferroelectric portion 322.

[0064] In an embodiment, the first ferroelectric portion 322 and the second ferroelectric portion 324 may be formed of substantially the same material, differing only in the concentration of oxygen vacancies. That is, each of the first ferroelectric portion 322 and the second ferroelectric portion 324 may include, for example, hafnium oxide, zirconium oxide, hafnium zirconium oxide, or a combination of two or more thereof. In an embodiment, when forming the first ferroelectric portion 322 on the first electrode layer 310, an oxygen source may be supplied. Then, when forming the second ferroelectric portion 324 on the first ferroelectric portion 322, the oxygen source may be reduced. As a result, oxygen deficiency may be generated within the second ferroelectric portion 324, and the concentration of oxygen vacancies in the second ferroelectric portion 324 may increase compared to the first ferroelectric portion 322. As an example, the first ferroelectric portion 322 and the second ferroelectric portion 324 may be formed by applying an atomic layer deposition (ALD) method.

[0065] In an embodiment, the thickness t2 of the second ferroelectric portion 324 may be less than the thickness t1 of the first ferroelectric portion 322. The thickness t2 of the second ferroelectric portion 324 may be 1 / 4 to 1 / 2 of the thickness t0 of the ferroelectric tunnel barrier layer 320.

[0066] Figure 8 and Figure 9 are diagrams schematically showing the operation of a semiconductor device according to an embodiment of the present disclosure. The method of operating a semiconductor device may be described using the Figure 7 semiconductor device 3. Figure 8 is a diagram showing a first write operation for converting the state of the semiconductor device 3 to an electrically conductive state. Figure 8 The internal structure and energy band diagram of the semiconductor device 3 after completion of the first write operation may be schematically shown. Figure 9FIG. is a diagram showing a second write operation for transitioning the semiconductor device 3 to an electrically-off state. Figure 9 The internal structure and energy band diagram of the semiconductor device 3 after completion of the second write operation can be schematically shown.

[0067] Referring to Figure 8 , a first write voltage can be applied between the first electrode layer 310 and the second electrode layer 330 to perform the first write operation of the semiconductor device 3. The first write voltage can be a voltage configured such that the bias applied to the second electrode layer 330 has a negative polarity and the bias applied to the first electrode layer 310 has a positive polarity.

[0068] Referring to Figure 8 , by applying the first write voltage, a polarization having a first polarization orientation P1 can be formed inside the ferroelectric tunnel barrier layer 320. The electric field generated by the polarization can induce electrons in the internal region of the second electrode layer 330 adjacent to the interface between the ferroelectric tunnel barrier layer 320 and the second electrode layer 330 to form an electron accumulation region 311.

[0069] In addition, when the first write voltage is applied between the first electrode layer 310 and the second electrode layer 330, oxygen vacancies having a positive polarity can accumulate inside the ferroelectric tunnel barrier layer 320 to form a conductive protrusion F320. The conductive protrusion F320 can grow inside the second ferroelectric portion 324 and extend from the interface between the second electrode layer 330 and the second ferroelectric portion 324 toward the first ferroelectric portion 322.

[0070] In an embodiment, the conductive protrusion F320 can be formed in the second ferroelectric portion 324 having a higher concentration of oxygen vacancies. The conductive protrusion F320 can stop growing after reaching the first ferroelectric portion 322 having a relatively lower concentration of oxygen vacancies. In an embodiment, referring to Figure 7 , the length of the conductive protrusion F320 along the thickness direction of the ferroelectric tunnel barrier layer 320 can correspond to the thickness t2 of the second ferroelectric portion 324.

[0071] As described above, the growth of the conductive protrusion F320 can be effectively controlled by utilizing the oxygen vacancy concentration difference between the first ferroelectric portion 322 and the second ferroelectric portion 324.

[0072] In Figure 8 , the shapes of the Fermi level Ef-330 and the conduction band level Ec-330 of the second electrode layer 330, the shape of the conduction band level Ec-320 of the ferroelectric tunnel junction layer 320, and the shape of the Fermi level Ef-310 of the first electrode layer 310 are the same as in Figure 2The shapes of the Fermi level Ef-130 and the conduction band level Ec-130 of the second electrode layer 130 shown, the shape of the conduction band level Ec-120 of the ferroelectric tunnel junction layer 120, and the shape of the Fermi level Ef-110 of the first electrode layer 110 are substantially the same. Due to the conductive protrusion F320, the tunneling width of the electrons tunneling for conduction can be reduced from a first width W3 corresponding to the thickness of the ferroelectric tunnel barrier layer 320 to a first tunneling width W-f2.

[0073] Referring to Figure 9 , by applying a second write voltage, a polarization having a second polarization orientation P2 can be formed in the ferroelectric tunnel barrier layer 320. The second write voltage can be a voltage configured such that the bias applied to the second electrode layer 330 has a positive polarity and the bias applied to the first electrode layer 310 has a negative polarity. The electric field generated by the polarization can form an electron-deficient region 312 in an internal region of the second electrode layer 330 adjacent to the interface between the ferroelectric tunnel barrier layer 320 and the second electrode layer 330.

[0074] In addition, when a second write voltage is applied between the first electrode layer 310 and the second electrode layer 330, the conductive protrusion F320 formed in the second ferroelectric portion 324 can be removed or can dissipate. The conductive protrusion F320 can be decomposed by discharging oxygen vacancies into the second ferroelectric portion 324 under the second write voltage. Although Figure 9 shows that the conductive protrusion F320 is completely removed by the second write voltage, the present disclosure is not limited thereto. In some embodiments, the conductive protrusion F320 can be partially removed. Under the second write voltage, the length in the layer thickness direction of the remaining conductive protrusion F320 can be shorter than Figure 8 the length of the conductive protrusion F320 in the layer thickness direction.

[0075] In Figure 9 , the shapes of the Fermi level Ef-330 and the conduction band level Ec-330 of the second electrode layer 330, the shape of the conduction band level Ec-320 of the ferroelectric tunnel junction layer 320, and the shape of the Fermi level Ef-310 of the first electrode layer 310 are substantially the same as the shapes of the Fermi level Ef-130 and the conduction band level Ec-130 of the second electrode layer 130, the shape of the conduction band level Ec-120 of the ferroelectric tunnel junction layer 120, and the shape of the Fermi level Ef-110 of the first electrode layer 110 shown in Figure 3 . When the electron-deficient region 312 is formed, the tunneling width through which electrons must tunnel for conduction can be increased from a first width W3 corresponding to the thickness of the ferroelectric tunnel barrier layer 320 to a second tunneling width W-r3.

[0076] As described above, according to an embodiment of the present disclosure, when performing the first write and second write operations, the position of the conductive protrusion F320 can be restricted to the second ferroelectric portion 324 of the ferroelectric tunnel barrier layer 320, thereby improving the reliability of the switching operation of the semiconductor device 3.

[0077] Figure 10 is a cross-sectional view schematically showing a semiconductor device according to another embodiment of the present disclosure. Compared with the semiconductor device 1 described with reference to Figure 1 the semiconductor device 4 may further include an oxygen storage layer 430.

[0078] The semiconductor device 4 may include a first electrode layer 410, a ferroelectric tunnel barrier layer 420 disposed on the first electrode layer 410, an oxygen storage layer 430 disposed on the ferroelectric tunnel barrier layer 420, and a second electrode layer 440 disposed on the oxygen storage layer 430.

[0079] The first electrode layer 410 may be substantially the same as the first electrode layer 110 of the semiconductor device 1 described above with reference to Figure 1 The ferroelectric tunnel barrier layer 420 may be substantially the same as the ferroelectric tunnel barrier layer 120 of the semiconductor device 1 described above with reference to Figure 1 The oxygen storage layer 430 may include a metal oxide that does not satisfy the stoichiometry. For example, the oxygen storage layer 430 may include titanium oxide, tantalum oxide, or a combination thereof. The oxygen storage layer 430 may exchange oxygen ions with the ferroelectric tunnel barrier layer 420.

[0080] The second electrode layer 440 may be disposed on the oxygen storage layer 430. The second electrode layer 440 may include a conductive material. In one embodiment, the second electrode layer 440 may be formed of substantially the same material as the first electrode layer 410. In another embodiment, the second electrode layer 440 may be formed of substantially the same material as the second electrode layer 130 of the semiconductor device 1 described above with reference to

[0081] In an embodiment, the first write operation and the second write operation of the semiconductor device 4 may be substantially the same as the first write operation and the second write operation of the semiconductor device 1 described above with reference to Figure 1 However, in the semiconductor device 4, when compared with the

[0082] semiconductor device 1, the oxygen storage layer 430 may be provided separately. Therefore, the generation of the conductive protrusion can be enhanced during the first write operation, and the decomposition of the conductive protrusion can be enhanced during the second write operation. The conductive protrusion may be arranged to extend from the interface between the oxygen storage layer 430 and the ferroelectric tunnel barrier layer 420 toward the first electrode layer 410 inside the ferroelectric tunnel barrier layer 420. Figure 1 However, in the semiconductor device 4, when compared with the Figure 1 semiconductor device 1, the oxygen storage layer 430 may be provided separately. Therefore, the generation of the conductive protrusion can be enhanced during the first write operation, and the decomposition of the conductive protrusion can be enhanced during the second write operation. The conductive protrusion may be arranged to extend from the interface between the oxygen storage layer 430 and the ferroelectric tunnel barrier layer 420 toward the first electrode layer 410 inside the ferroelectric tunnel barrier layer 420.

[0083] Figure 11 is a cross-sectional view schematically showing a semiconductor device according to still another embodiment of the present disclosure. Referring to Figure 11 , compared with the semiconductor device 4 described with reference to Figure 10 , the semiconductor device 5 may further include a protruding control layer 524 provided as a part of the ferroelectric tunnel barrier layer 520.

[0084] The semiconductor device 5 may include a first electrode layer 510, a ferroelectric tunnel barrier layer 520 provided on the first electrode layer 510, an oxygen storage layer 530 provided on the ferroelectric tunnel barrier layer 520, and a second electrode layer 540 provided on the oxygen storage layer 530. The configurations of the first electrode layer 510, the oxygen storage layer 530, and the second electrode layer 540 may be substantially the same as those of the first electrode layer 410, the oxygen storage layer 430, and the second electrode layer 440 of the semiconductor device 4 described with reference to Figure 10 .

[0085] The ferroelectric tunnel barrier layer 520 may include a first ferroelectric layer 522a, a protruding control layer 524, and a second ferroelectric layer 522b sequentially provided on the first electrode layer 510. The configurations of the first ferroelectric layer 522a, the protruding control layer 524, and the second ferroelectric layer 522b may be substantially the same as those of the first ferroelectric layer 222a, the protruding control layer 224, and the second ferroelectric layer 222b of the semiconductor device 2 described with reference to Figure 4 , and thus, detailed descriptions thereof are omitted.

[0086] Figure 12 is a cross-sectional view schematically showing a semiconductor device according to still another embodiment of the present disclosure. When compared with the semiconductor device 4 described with reference to Figure 10 , the semiconductor device 6 may have a different ferroelectric tunnel barrier layer configuration.

[0087] The semiconductor device 6 may include a first electrode layer 610, a ferroelectric tunnel barrier layer 620 provided on the first electrode layer 610, an oxygen storage layer 630, and a second electrode layer 640 provided on the oxygen storage layer 630. The configurations of the first electrode layer 610, the oxygen storage layer 630, and the second electrode layer 640 may be substantially the same as those of the first electrode layer 410, the oxygen storage layer 430, and the second electrode layer 440 of the semiconductor device 4 described with reference to Figure 10 , and thus, detailed descriptions thereof are omitted.

[0088] The ferroelectric tunnel barrier layer 620 may include a first ferroelectric portion 622 and a second ferroelectric portion 624 sequentially provided on the first electrode layer 610. The configurations of the first ferroelectric portion 622 and the second ferroelectric portion 624 may be substantially the same as those of the first ferroelectric portion 322 and the second ferroelectric portion 324 of the semiconductor device 3 described with reference to Figure 7 , and thus, detailed descriptions thereof are omitted.

[0089] Referring to Figure 12 , the second ferroelectric portion 624 can be set to contact the oxygen storage layer 630. Accordingly, a conductive protrusion generated in relation to the operation of the semiconductor device 6 can extend from the interface between the oxygen storage layer 630 and the second ferroelectric portion 624 toward the first ferroelectric portion 622 and into the interior of the second ferroelectric portion 624.

[0090] The concepts have been disclosed in connection with some embodiments as described above. Those skilled in the art will understand that various modifications, additions, and substitutions are possible without departing from the scope and spirit of the present disclosure. Accordingly, the embodiments disclosed in this specification should not be considered from a restrictive perspective but from an illustrative perspective. The scope of the concepts is not limited to the above description but is defined by the appended claims, and all distinguishing features within the equivalent scope should be construed as being included in the concepts.

Claims

1. A semiconductor device, comprising: a first electrode layer; a ferroelectric tunnel barrier layer disposed on the first electrode layer, the ferroelectric tunnel barrier layer comprising oxygen vacancies; and a second electrode layer disposed on the ferroelectric tunnel barrier layer and comprising a metal oxide, Wherein, compared with the first electrode layer, the second electrode layer has a relatively low conductive carrier density.

2. The semiconductor device according to claim 1, further comprising a conductive protrusion extending from an interface between the second electrode layer and the ferroelectric tunnel barrier layer into the ferroelectric tunnel barrier layer, in, The conductive protrusions include oxygen vacancies.

3. The semiconductor device according to claim 2, wherein: The conductive protrusion does not contact the first electrode layer.

4. The semiconductor device according to claim 1, wherein: The first electrode layer includes an inert metal.

5. The semiconductor device according to claim 1, wherein The metal oxide includes at least one selected from the group consisting of ruthenium oxide RuO2, iridium oxide IrO2, platinum oxide PtO2, strontium ruthenium oxide SrRuO3, metal perovskite oxides and conductive pyrochlore oxides.

6. The semiconductor device according to claim 1, wherein The ferroelectric tunnel barrier layer includes at least one of hafnium oxide, zirconium oxide and hafnium zirconium oxide.

7. The semiconductor device according to claim 1, wherein The ferroelectric tunnel barrier layer comprises: a first ferroelectric layer disposed adjacent to the first electrode layer; a second ferroelectric layer disposed adjacent to the second electrode layer; and A protruding control layer is disposed between the first ferroelectric layer and the second ferroelectric layer.

8. The semiconductor device according to claim 7, wherein: The distance from the second electrode layer to the protrusion control layer is 1 / 4 to 1 / 2 of the distance between the first electrode layer and the second electrode layer.

9. The semiconductor device according to claim 7, wherein: The protrusion control layer includes amorphous silicon oxide or amorphous aluminum oxide.

10. The semiconductor device according to claim 1, in, The ferroelectric tunnel barrier layer comprises: a first ferroelectric portion comprising a first concentration of oxygen vacancies; and a second ferroelectric portion including a second concentration of oxygen vacancies, the second concentration being higher than the first concentration, and The second ferroelectric portion is arranged closer to the second electrode layer than the first ferroelectric portion.

11. The semiconductor device according to claim 10, wherein: The ferroelectric tunnel barrier layer includes a conductive protrusion disposed in the second ferroelectric portion.

12. The semiconductor device according to claim 10, wherein: The thickness of the second ferroelectric portion is 1 / 4 to 1 / 2 of the thickness of the ferroelectric tunnel barrier layer.

13. A semiconductor device comprising: a first electrode layer; A ferroelectric tunnel barrier layer, which is disposed on the first electrode layer, and the ferroelectric tunnel barrier layer includes oxygen vacancies; an oxygen storage layer, which is disposed on the ferroelectric tunnel barrier layer; as well as The second electrode layer is disposed on the oxygen storage layer.

14. The semiconductor device according to claim 13, further comprising a conductive protrusion extending from the oxygen storage layer to the ferroelectric tunnel barrier layer, in, The conductive protrusions include oxygen vacancies.

15. The semiconductor device according to claim 14, wherein: The conductive protrusion does not contact the first electrode layer.

16. The semiconductor device according to claim 13, in, The oxygen storage layer includes a metal oxide that does not satisfy a stoichiometric ratio, and Wherein, the oxygen storage layer includes at least one selected from titanium oxide and tantalum oxide.

17. The semiconductor device according to claim 13, wherein: The ferroelectric tunnel barrier layer comprises: a first ferroelectric layer disposed adjacent to the first electrode layer; a second ferroelectric layer disposed adjacent to the oxygen storage layer; and a protruding control layer disposed between the first ferroelectric layer and the second ferroelectric layer, Wherein, the second ferroelectric layer includes a conductive protrusion containing oxygen vacancies.

18. The semiconductor device according to claim 17, wherein: The protrusion control layer includes amorphous silicon oxide or amorphous aluminum oxide.

19. The semiconductor device according to claim 13, in, The ferroelectric tunnel barrier layer comprises: a first ferroelectric portion having a relatively low concentration of oxygen vacancies; and a second ferroelectric portion having a relatively high concentration of oxygen vacancies, and Wherein, the second ferroelectric portion is arranged adjacent to the second electrode layer.

20. The semiconductor device according to claim 19, wherein The ferroelectric tunnel barrier layer includes a conductive protrusion disposed in the second ferroelectric portion.

21. A semiconductor device comprising: a first electrode layer; a ferroelectric tunnel barrier layer, disposed on the first electrode layer; as well as a second electrode layer disposed on the ferroelectric tunnel barrier layer and comprising a metal oxide, Wherein, the ferroelectric tunnel barrier layer comprises: a first ferroelectric portion comprising a first concentration of oxygen vacancies; and A second ferroelectric portion includes a second concentration of oxygen vacancies, the second concentration being higher than the first concentration.

22. The semiconductor device according to claim 21, wherein The ferroelectric tunnel barrier layer includes a conductive protrusion disposed in the second ferroelectric portion, and Wherein, the conductive protrusions include oxygen vacancies.

23. The semiconductor device according to claim 21, in, The first ferroelectric portion is disposed adjacent to the first electrode layer, and Wherein, the second ferroelectric portion is arranged adjacent to the second electrode layer.

24. The semiconductor device according to claim 21, wherein The thickness of the second ferroelectric portion is 1 / 4 to 1 / 2 of the thickness of the ferroelectric tunnel barrier layer. 25 . The semiconductor device according to claim 21 , further comprising an oxygen storage layer provided between the first electrode layer and the second electrode layer and in contact with the second ferroelectric portion.

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