Isolation Devices

Abstract

To provide an insulation device capable of improving reliability.SOLUTION: An insulation device comprises: a first electrode; a second electrode; and an insulating film provided between the first electrode and the second electrode. The insulating film has a positive charged region. The positive charged region is arranged at a portion in a direction from the first electrode toward the second electrode, in the insulating film.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The embodiments relate to an isolation device. [Background technology]

[0002] In an insulating device such as a digital isolator, a pair of electrodes is insulated from each other via a thick insulating film to ensure high electric field resistance. In such an insulating device, there is a problem that the electric field concentrates at the ends of the electrodes, reducing reliability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-129657 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the embodiments is to provide an isolation device that can improve reliability. [Means for solving the problem]

[0005] An insulating device according to an embodiment includes a first electrode, a second electrode, and an insulating film provided between the first electrode and the second electrode. The insulating film has a positively charged region. The positively charged region is located in a portion of the insulating film in a direction from the first electrode to the second electrode. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a cross-sectional view showing an insulating device according to a first embodiment. [Diagram 2]2(a) is a partial cross-sectional view showing region A in FIG. 1, (b) is a graph showing the potential distribution in the insulating film with position on the vertical axis and potential on the horizontal axis, (c) is a graph showing the electric field strength distribution in the insulating film with position on the vertical axis and electric field strength on the horizontal axis, (d) is a partial cross-sectional view showing region A in FIG. 1, (e) is a graph showing the potential distribution in the insulating film with position on the vertical axis and potential on the horizontal axis, and (f) is a graph showing the electric field strength distribution in the insulating film with position on the vertical axis and electric field strength on the horizontal axis. [Diagram 3] Figure 3(a) is a partial cross-sectional view showing an insulating device according to the second embodiment, (b) is a graph showing the potential distribution in the insulating film with position on the vertical axis and potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with position on the vertical axis and electric field strength on the horizontal axis. [Figure 4] FIG. 4(a) is a partial cross-sectional view showing an insulating device according to the second embodiment, (b) is a graph showing the potential distribution in the insulating film with the position on the vertical axis and the electric field strength on the horizontal axis, and FIG. 4(c) is a graph showing the effect of positive charges on the electric field strength distribution with the density of positive charges in the positively charged region on the horizontal axis and the electric field reduction rate (E / E0) on the vertical axis. [Diagram 5] 5(a) and (b) are diagrams showing the molecular structure of silicon oxide, where (a) shows a state without oxygen vacancies and (b) shows a state with oxygen vacancies. [Figure 6] 6(a) and (b) are graphs showing peaks corresponding to the silicon 2p core level in the XPS analysis results of silicon oxide, with the horizontal axis representing binding energy and the vertical axis representing intensity, where (a) shows the case where the concentration of oxygen vacancies is low, and (b) shows the case where the concentration of oxygen vacancies is high. [Figure 7] FIG. 7 is a graph showing the effect of oxygen vacancies on the amount of peak shift, with the concentration of oxygen vacancies on the horizontal axis and the amount of peak shift on the vertical axis. [Figure 8]Figure 8(a) is a partial cross-sectional view showing an insulating device according to the third embodiment, (b) is a graph showing the potential distribution in the insulating film with position on the vertical axis and potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with position on the vertical axis and electric field strength on the horizontal axis. [Figure 9] Figure 9(a) is a partial cross-sectional view showing an insulating device according to the fourth embodiment, (b) is a graph showing the potential distribution in the insulating film with position on the vertical axis and potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with position on the vertical axis and electric field strength on the horizontal axis. [Figure 10] Figure 10(a) is a partial cross-sectional view showing an insulating device according to the fifth embodiment, (b) is a graph showing the potential distribution in the insulating film with position on the vertical axis and potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with position on the vertical axis and electric field strength on the horizontal axis. [Figure 11] 11(a) is a partial cross-sectional view showing an insulating device according to a reference example, (b) is a graph showing the potential distribution along the dotted-dash line B shown in FIG. 11(a) with position on the vertical axis and potential on the horizontal axis, (c) is a graph showing the electric field strength distribution along the dotted-dash line B shown in FIG. 11(a) with position on the vertical axis and electric field strength on the horizontal axis, (d) is a partial cross-sectional view showing an insulating device according to the sixth embodiment, (e) is a graph showing the potential distribution along the dotted-dash line B shown in FIG. 11(d) with position on the vertical axis and potential on the horizontal axis, and (f) is a graph showing the electric field strength distribution along the dotted-dash line B shown in FIG. 11(d) with position on the vertical axis and electric field strength on the horizontal axis. [Figure 12] Figure 12(a) is a partial cross-sectional view showing an insulating device according to the seventh embodiment, (b) is a graph showing the potential distribution in the insulating film with position on the vertical axis and potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with position on the vertical axis and electric field strength on the horizontal axis. [Figure 13]FIG. 13(a) is a partial cross-sectional view showing an insulating device according to a first variant of the seventh embodiment, (b) is a graph showing the potential distribution in the insulating film with the position on the vertical axis and the potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with the position on the vertical axis and the electric field strength on the horizontal axis. [Figure 14] FIG. 14(a) is a partial cross-sectional view showing an insulating device according to a second variant of the seventh embodiment, (b) is a graph showing the potential distribution in the insulating film with the position on the vertical axis and the potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with the position on the vertical axis and the electric field strength on the horizontal axis. [Figure 15] FIG. 15 is a partial cross-sectional view showing an insulating device according to the eighth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] <First embodiment> FIG. 1 is a cross-sectional view showing an insulating device according to the present embodiment. The isolation device 1 according to this embodiment is, for example, a magnetic isolation type or capacitive isolation type digital isolator.

[0008] As shown in FIG. 1, an insulating device 1 includes a lower electrode 11, and an upper electrode 12 is provided on the lower electrode 11, the upper electrode 12 being spaced apart from the lower electrode 11. The lower electrode 11 and the upper electrode 12 are, for example, coils. An insulating film 10 is provided between the lower electrode 11 and the upper electrode 12. Note that all the drawings are schematic diagrams and do not necessarily strictly correspond to actual products. For example, in FIG. 1, five lower electrodes 11 and five upper electrodes 12 are depicted, but the number of each electrode may be six or more or four or less, and may be an even number or an odd number.

[0009] The insulating film 10 includes, for example, silicon (Si) and oxygen (O), and includes, for example, silicon oxide. A positively charged region 21 is provided in the insulating film 10. The positively charged region 21 includes a positive charge and is positively charged. The charge density of the positively charged region is 1×10 16 cm-3 As described later, the positive charge is formed by, for example, oxygen vacancies in silicon oxide, corona discharge, or hafnium oxide.

[0010] When the positively charged region 21 is generated by oxygen deficiency, the oxygen concentration in the positively charged region 21 is lower than the oxygen concentration in the region other than the positively charged region 21 in the insulating film 10. For example, the positively charged region 21 is formed of SiO x (x is less than 2), and the regions of the insulating film 10 other than the positively charged regions 21 are made of SiO 2 .

[0011] The direction from the lower electrode 11 toward the upper electrode 12 is defined as the "vertical direction D." The positively charged region 21 is disposed in a portion of the insulating film 10 in the vertical direction D. The thickness of the insulating film 10 in the vertical direction D is, for example, several μm to several tens of μm.

[0012] A ground electrode 13 is provided around the lower electrode 11. A plurality of vias 15 are provided around a portion 14 of the insulating film 10 located between the lower electrode 11 and the upper electrode 12. The vias 15 are connected to the ground electrode 13. The vias 15 function as a magnetic shield. The ground electrode 13 and the vias 15 do not necessarily have to be provided.

[0013] 2(a) is a partial cross-sectional view showing region A in FIG. 1, (b) is a graph showing the potential distribution in the insulating film with position on the vertical axis and potential on the horizontal axis, (c) is a graph showing the electric field strength distribution in the insulating film with position on the vertical axis and electric field strength on the horizontal axis, (d) is a partial cross-sectional view showing region A in FIG. 1, (e) is a graph showing the potential distribution in the insulating film with position on the vertical axis and potential on the horizontal axis, and (f) is a graph showing the electric field strength distribution in the insulating film with position on the vertical axis and electric field strength on the horizontal axis.

[0014] 2(a) to (c) show, as a reference example, a case where a positively charged region 21 is not provided. FIG. 2(d) to (f) show, as the present embodiment, a case where a positively charged region 21 is provided. The positions represented by the vertical axes of FIG. 2(b) and (c) correspond to FIG. 2(a). The positions represented by the vertical axes of FIG. 2(e) and (f) correspond to FIG. 2(d). In FIG. 2(d), a positive charge is represented by a symbol "+" surrounded by a circle. This is the same in similar figures described later. In FIG. 2(e) and (f), the graphs shown in FIG. 2(b) and (c), respectively, are shown by dashed lines.

[0015] When the insulating device 1 operates, a signal having a higher potential than that of the lower electrode 11 is input to the upper electrode 12. A ground potential is applied to the ground electrode 13. As a result, when a positively charged region 21 is not provided in the insulating film 10 as shown in FIG. 2(a), the potential distribution becomes linear as shown in FIG. 2(b), and the electric field strength becomes constant as shown in FIG. 2(c). However, since the electric field is concentrated near the corner 16 of the upper electrode 12 shown in FIG. 1, the electric field strength is higher than other parts as shown by the two-dot chain line in FIG. 2(c). Therefore, impact ionization occurs near the corner 16 of the insulating film 10, and avalanche breakdown may occur.

[0016] In contrast, as shown in FIG. 2(d), in the insulating device 1 according to this embodiment, a positively charged region 21 is provided in the insulating film 10. Therefore, as shown in FIG. 2(e), the potential of the positively charged region 21 in the insulating film 10 increases. As a result, as shown in FIG. 2(f), the electric field strength distribution is no longer linear, and the electric field strength increases in the portion of the insulating film 10 closer to the lower electrode 11 than the positively charged region 21, but decreases in the portion of the insulating film 10 closer to the upper electrode 12. This makes it possible to suppress an increase in the electric field strength in the vicinity of the corner 16. As a result, avalanche breakdown is less likely to occur, and the reliability of the insulating device 1 is improved.

[0017] Thus, according to this embodiment, by providing the positively charged region 21 in the insulating film 10, it is possible to suppress electric field concentration in the vicinity of the corners 16 of the upper electrode 12 and improve the reliability of the insulating device 1. In the lower electrode 11, the electric field concentration at the corners is alleviated by the ground electrode 13 arranged around the lower electrode 11.

[0018] A method for forming positive charges in the insulating film 10 will be described below. First, a method for forming a positive charge by oxygen deficiency will be described. The insulating film 10 is formed, for example, by depositing silicon oxide by plasma CVD (Chemical Vapor Deposition). A mixed gas of silane (SiH4), nitrous oxide (N2O), oxygen (O2), etc. is used as a source for the plasma CVD. Then, at the timing of forming the positively charged region 21, the composition of the source is changed so that it contains more nitrogen (N) and less oxygen (O). After the formation of the positively charged region 21 is completed, the source composition is returned to the original. In this way, the insulating film 10 including the positively charged region 21 is formed.

[0019] Next, a method for generating a positive charge by corona discharge will be described. Silicon oxide is deposited by plasma CVD to form the insulating film 10 partially. Next, the intermediate structure is removed from the plasma CVD apparatus at the timing when the positively charged region 21 is to be formed, and corona discharge is applied. As a result, positive charges are accumulated on the exposed surface of the insulating film 10 in the intermediate structure. Next, the intermediate structure is returned to the plasma CVD apparatus, and silicon oxide is deposited by plasma CVD. As a result, the insulating film 10 including the positively charged region 21 is formed.

[0020] Next, a method for forming a positive charge using hafnium oxide will be described. The insulating film 10 is partially formed by depositing silicon oxide by plasma CVD. Next, the intermediate structure is removed from the plasma CVD apparatus at the timing when the positively charged region 21 is to be formed, and hafnium oxide (HfO2) is deposited by ALD (Atomic Layer Deposition). This layer of hafnium oxide becomes the positively charged region 21. Next, the intermediate structure is returned to the plasma CVD apparatus, and silicon oxide is deposited by plasma CVD. As a result, the insulating film 10 including the positively charged region 21 is formed.

[0021] <Second embodiment> Figure 3(a) is a partial cross-sectional view showing an insulating device of this embodiment, (b) is a graph showing the potential distribution in the insulating film with the position on the vertical axis and the potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with the position on the vertical axis and the electric field strength on the horizontal axis. The region shown in Figure 3(a) corresponds to region A in Figure 1. The positions indicated by the vertical axes in Figures 3(b) and (c) correspond to Figure 3(a). In Figures 3(b) and (c), the graphs shown in Figures 2(b) and (c), respectively, are indicated by dashed lines.

[0022] As shown in FIG. 3(a), in the insulating device 2 according to this embodiment, the thickness t of the positively charged region 21 in the vertical direction D is thicker than that of the insulating device 1 according to the first embodiment. Therefore, as shown in FIG. 3(b), the thickness of the portion in the insulating film 10 where the electric potential increases is thicker. As a result, as shown in FIG. 3(c), the change in the electric field intensity becomes gentler. Furthermore, by increasing the thickness t, the amount of charge contained in the positively charged region 21 increases. The thickness t, i.e., the length of the positively charged region 21 along the vertical direction D, is preferably 500 nm or more.

[0023] FIG. 4(a) is a partial cross-sectional view showing an insulating device according to this embodiment, and (b) is a graph showing the potential distribution in an insulating film, with the vertical axis representing position and the horizontal axis representing electric field intensity. 4(a) and (b), when the positively charged region 21 is not provided, the electric field strength at the interface of the insulating film 10 with the upper electrode 12 is set to E0, and when the positively charged region 21 is provided, the electric field strength at the interface of the insulating film 10 with the upper electrode 12 is set to E. Then, the value (E / E0) is defined as the electric field reduction rate caused by the positively charged region 21.

[0024] FIG. 4(c) is a graph showing the effect of positive charge on the electric field intensity distribution, with the horizontal axis representing the density of positive charge in the positively charged region and the vertical axis representing the electric field reduction rate (E / E0). As shown in FIG. 4(c), when the density of positive charges in the positively charged region 21 increases, the electric field reduction ratio (E / E0) decreases. In the example shown in FIG. 4(c), when the density of positive charges is 1×10 16 cm -3 If the density of positive charges is 1×10 or more, a decrease in the electric field reduction rate (E / E0) is observed. 17 cm -3 If the electric field reduction rate is equal to or higher than this, the electric field reduction rate (E / E0) is equal to or lower than 0.8. It is preferable that the electric field reduction rate is set to a level that can offset the electric field concentration at the corners 16. Other than the above, the configuration, operation, and effects of this embodiment are the same as those of the first embodiment.

[0025] An example of a method for evaluating the density of positive charges in the positively charged area 21 will now be described. 5(a) and (b) are diagrams showing the molecular structure of silicon oxide, where (a) shows a state without oxygen vacancies and (b) shows a state with oxygen vacancies. As shown in Figure 5(a), when there is no oxygen vacancy, one silicon atom is bonded to four oxygen atoms. In contrast, as shown in Figure 5(b), when there is an oxygen vacancy, one silicon atom is bonded to three oxygen atoms, and one bond of the silicon atom is dangling.

[0026] 6(a) and (b) are graphs showing peaks corresponding to the silicon 2p core level (Si 2p) in XPS (X-ray Photoelectron Spectroscopy) analysis results of silicon oxide, with the horizontal axis representing binding energy and the vertical axis representing detection intensity, where (a) shows the case where the concentration of oxygen vacancies is low, and (b) shows the case where the concentration of oxygen vacancies is high. The oxygen vacancy concentration of the sample shown in FIG. 6(b) is about five times that of the sample shown in FIG. 6(a). As shown in FIGS. 6(a) and 6(b), when the concentration of oxygen vacancies in silicon oxide increases, the peak corresponding to the silicon 2p core level shifts to the higher potential side.

[0027] FIG. 7 is a graph showing the effect of oxygen vacancies on the amount of peak shift, with the concentration of oxygen vacancies on the horizontal axis and the amount of peak shift on the vertical axis. The horizontal axis in FIG. 7 represents the relative value of the peak intensity near 2250 eV in the XPS analysis, and the intensity of this peak has a positive correlation with the concentration of oxygen vacancies.

[0028] 7, the higher the oxygen vacancy concentration in the silicon oxide, the larger the peak shift amount. Therefore, by performing XPS analysis on the positively charged region 21 in the insulating film 10, the oxygen vacancy concentration can be estimated from the peak shift amount, and the positive charge amount can be estimated.

[0029] <Third embodiment> Figure 8(a) is a partial cross-sectional view showing an insulating device of this embodiment, (b) is a graph showing the potential distribution in the insulating film with the position on the vertical axis and the potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with the position on the vertical axis and the electric field strength on the horizontal axis. The region shown in Fig. 8(a) corresponds to region A in Fig. 1. The positions indicated by the vertical axes in Fig. 8(b) and (c) correspond to Fig. 8(a). In Fig. 8(b) and (c), the graphs shown in Fig. 2(b) and (c), respectively, are indicated by dashed lines. The same applies to similar figures described later.

[0030] 8(a), in the insulating device 3 according to this embodiment, the positively charged region 21 is located on the upper electrode 12 side. More specifically, the positively charged region 21 is located between the upper electrode 12 and a midpoint 17 between the lower electrode 11 and the upper electrode 12. The positively charged region 21 may be in contact with the upper electrode 12 or may be separated therefrom.

[0031] 8(b) and (c), according to this embodiment, it is possible to effectively reduce the electric field strength in the insulating film 10 near the upper electrode 12. This makes it possible to more effectively suppress electric field concentration near the corners 16 of the upper electrode 12. Other configurations, operations, and effects of this embodiment are similar to those of the first embodiment.

[0032] <Fourth embodiment> Figure 9(a) is a partial cross-sectional view showing an insulating device of this embodiment, (b) is a graph showing the potential distribution in the insulating film with the position on the vertical axis and the potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with the position on the vertical axis and the electric field strength on the horizontal axis.

[0033] 9(a), in the insulating device 4 according to this embodiment, the positively charged region 21 is located on the lower electrode 11 side. More specifically, the positively charged region 21 is located between the lower electrode 11 and a midpoint 17 between the lower electrode 11 and the upper electrode 12. The positively charged region 21 may be in contact with the lower electrode 11 or may be separated therefrom.

[0034] 9(b) and (c), according to this embodiment, the electric field intensity can be reduced over a wide region between the positively charged region 21 in the insulating film 10 and the upper electrode 12. Other configurations, operations, and effects of this embodiment are similar to those of the first embodiment.

[0035] <Fifth embodiment> Figure 10(a) is a partial cross-sectional view showing an insulating device of this embodiment, (b) is a graph showing the potential distribution in the insulating film with the position on the vertical axis and the potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with the position on the vertical axis and the electric field strength on the horizontal axis.

[0036] As shown in Fig. 10(a), in the insulating device 5 according to this embodiment, in addition to the positively charged region 21, a negatively charged region 22 is provided in the insulating film 10. Negative charges are accumulated in the negatively charged region 22. In Fig. 10(a), the negative charges are represented by a circle surrounding the symbol "-". This also applies to similar figures described later. The negative charges are accumulated by, for example, corona discharge.

[0037] In this embodiment, negatively charged region 22 is disposed closer to lower electrode 11 than positively charged region 21. That is, negatively charged region 22 is located between lower electrode 11 and positively charged region 21. Negatively charged region 22 may be in contact with positively charged region 21 or may be separated from it.

[0038] 10(b), in the insulating device 5, the potential increases in the positively charged region 21 and decreases in the negatively charged region 22. This makes it possible to reduce the electric field strength not only in the vicinity of the upper electrode 12 but also in the vicinity of the lower electrode 11, as shown in FIG. 10(c). As a result, the reliability of the insulating device 5 is further improved.

[0039] Thus, according to this embodiment, by providing the negatively charged region 22 and the positively charged region 21 in the insulating film 10, it is possible to suppress electric field concentration in the vicinity of the lower electrode 11 and the upper electrode 12, and improve the reliability of the insulating device 5. Other configurations, operations, and effects of this embodiment are similar to those of the first embodiment.

[0040] Sixth embodiment 11(a) is a partial cross-sectional view showing an insulating device according to a reference example, (b) is a graph showing the potential distribution along the dotted-dash line B shown in FIG. 11(a) with position on the vertical axis and potential on the horizontal axis, (c) is a graph showing the electric field strength distribution along the dotted-dash line B shown in FIG. 11(a) with position on the vertical axis and electric field strength on the horizontal axis, (d) is a partial cross-sectional view showing an insulating device according to this embodiment, (e) is a graph showing the potential distribution along the dotted-dash line B shown in FIG. 11(d) with position on the vertical axis and potential on the horizontal axis, and (f) is a graph showing the electric field strength distribution along the dotted-dash line B shown in FIG. 11(d) with position on the vertical axis and electric field strength on the horizontal axis.

[0041] 11(a)-(c) show a reference example in which the positively charged region 21 and the negatively charged region 22 are not provided. FIG. 11(d)-(f) show the present embodiment in which the positively charged region 21 and the negatively charged region 22 are provided. The positions indicated by the vertical axes of FIG. 11(b) and (c) correspond to FIG. 11(a). The positions indicated by the vertical axes of FIG. 11(e) and (f) correspond to FIG. 11(d). In FIG. 11(e) and (f), the graphs shown in FIG. 11(b) and (c) are shown by dashed lines. Note that in FIG. 11(b) and (e), the influence of the corners of the lower electrode 11 and the upper electrode 12 is not taken into consideration, but in FIG. 11(c) and (f), the influence of the corners is taken into consideration. The same applies to similar figures described later.

[0042] 11(a) to 11(c), if the positively charged regions 21 and the negatively charged regions 22 were not provided, the electric field would concentrate near the ends of the lower electrode 11 and the upper electrode 12 in the insulating film 10, increasing the electric field strength. This makes avalanche breakdown more likely to occur in these regions.

[0043] In contrast, as shown in FIG. 11(d), in the insulating device 6 according to this embodiment, in the insulating film 10, a negatively charged region 22 is disposed near the lower electrode 11, and a positively charged region 21 is disposed near the upper electrode 12. More specifically, the negatively charged region 22 is located between the lower electrode 11 and the midpoint 17 between the lower electrode 11 and the upper electrode 12. The negatively charged region 22 may be in contact with the lower electrode 11 or may be separated from it. On the other hand, the positively charged region 21 is located between the midpoint 17 and the upper electrode 12. The positively charged region 21 may be in contact with the upper electrode 12 or may be separated from it. The positively charged region 21 is separated from the negatively charged region 22.

[0044] 11(e), the potential in the insulating film 10 decreases near the lower electrode 11 and increases near the upper electrode 12. As a result, as shown in FIG 11(f), the electric field intensity in the insulating film 10 decreases near the lower electrode 11 and near the upper electrode 12, and the electric field concentration at the ends is alleviated. As a result, avalanche breakdown is less likely to occur, and the reliability of the insulating device 6 is improved. Other configurations, operations, and effects of this embodiment are similar to those of the first embodiment.

[0045] Seventh embodiment Figure 12(a) is a partial cross-sectional view showing an insulating device of this embodiment, (b) is a graph showing the potential distribution in the insulating film with the position on the vertical axis and the potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with the position on the vertical axis and the electric field strength on the horizontal axis.

[0046] 12(a), in an insulating device 7 according to this embodiment, a plurality of positively charged regions 21 and a plurality of negatively charged regions 22 are arranged alternately in an insulating film 10 along a vertical direction D. In a stack consisting of a plurality of positively charged regions 21 and a plurality of negatively charged regions 22, a negatively charged region 22a is disposed at a position closest to a lower electrode 11, and a positively charged region 21a is disposed at a position closest to an upper electrode 12.

[0047] As a result, the potential distribution along the vertical direction D becomes wavy as shown in Fig. 12(b), and the electric field intensity distribution along the vertical direction D also becomes wavy as shown in Fig. 12(c). As a result, compared to the sixth embodiment shown in Fig. 11(f), the electric field in the portion between the positively charged region 21a and the negatively charged region 22a in the insulating film 10 can be alleviated. Other configurations, operations, and effects of this embodiment are similar to those of the first embodiment.

[0048] <First Modification of the Seventh Embodiment> Figure 13(a) is a partial cross-sectional view showing an insulating device of this modified example, (b) is a graph showing the potential distribution in the insulating film with the position on the vertical axis and the potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with the position on the vertical axis and the electric field strength on the horizontal axis.

[0049] As shown in FIG. 13(a), in the insulating device 7a according to this modification, the distribution of charge amount is different compared to the insulating device 7 according to the seventh embodiment (see FIG. 12(a)). More specifically, the amount of positive charge of the multiple positively charged regions 21, excluding the charged region 21a closest to the upper electrode 12, is less than the amount of positive charge of the positively charged region 21a closest to the upper electrode 12. Similarly, the amount of negative charge of the multiple negatively charged regions 22, excluding the charged region 22a closest to the lower electrode 11, is less than the amount of negative charge of the negatively charged region 22a closest to the lower electrode 11.

[0050] This makes it possible to reduce the amplitude of the electric field strength in the portion between the positively charged region 21a and the negatively charged region 22a in the insulating film 10. Depending on the usage conditions of the insulating device, it is effective to adjust the distribution of the charge amount according to the position, as in this modified example. Other configurations, operations, and effects of this modified example are the same as those of the seventh embodiment.

[0051] <Second Modification of the Seventh Embodiment> Figure 14(a) is a partial cross-sectional view showing an insulating device of this modified example, (b) is a graph showing the potential distribution in the insulating film with position on the vertical axis and potential on the horizontal axis, and (c) is a graph showing the electric field strength distribution in the insulating film with position on the vertical axis and electric field strength on the horizontal axis.

[0052] As shown in FIG. 14(a), in an insulating device 7b according to this modification, the arrangement period of the positively charged regions 21 and the negatively charged regions 22 in the vertical direction D is shorter than that of the insulating device 7 according to the seventh embodiment (see FIG. 12(a)). This makes it possible to reduce the amplitude of the electric field strength in the portion between the positively charged regions 21a and the negatively charged regions 22a in the insulating film 10. Depending on the usage conditions of the insulating device, it may be effective to adjust the arrangement period of the charged regions as in this modification. Other than the above, the configuration, operation, and effects of this modification are the same as those of the seventh embodiment.

[0053] <Eighth embodiment> FIG. 15 is a partial cross-sectional view showing an insulating device according to this embodiment. This embodiment is an example in which the positively charged region 23 is formed by hafnium oxide rather than oxygen vacancies in silicon oxide.

[0054] As shown in FIG. 15, in an insulating device 8 according to this embodiment, a positively charged region 23 is provided in an insulating film 10. The positively charged region 23 contains hafnium (Hf) and oxygen (O), for example, hafnium oxide (HfO2). A portion of the insulating film 10 other than the positively charged region 23 contains silicon (Si) and oxygen (O), for example, silicon oxide (SiO2). This also makes it possible to realize a positively charged region in the insulating film 10 and obtain the same effect as in the first embodiment. The configuration, operation, and effect of this embodiment other than those described above are the same as those of the first embodiment.

[0055] According to the embodiment described above, an insulating device capable of improving reliability can be realized.

[0056] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. In addition, the above-mentioned embodiments and their modifications can be implemented in combination with each other. [Explanation of symbols]

[0057] 1, 2, 3, 4, 5, 6, 7, 7a, 7b, 8: Isolation devices 10: Insulating film 11: Lower electrode 12: Upper electrode 13: Ground electrode 14: Part 15: Beer 16: Corner 17: Midpoint 21, 21a: positively charged area 22, 22a: negatively charged area 23: Positively charged area D: Vertical direction t: thickness

Claims

1. A first electrode; A second electrode; an insulating film provided between the first electrode and the second electrode, the insulating film having a positively charged region disposed in a portion in a direction from the first electrode to the second electrode; Equipped with An insulating device, wherein the charge density of the positively charged region is 1×10 16 cm −3 or greater.

2. 2. The isolation device of claim 1, wherein the positively charged region is located between the second electrode and a midpoint between the first electrode and the second electrode.

3. 3. The insulating device according to claim 1, wherein the insulating film further includes a negatively charged region disposed in another portion in the direction.

4. 4. The isolation device of claim 3, wherein the negatively charged region is located between the first electrode and the positively charged region.

5. 4. The insulating device of claim 3, wherein a plurality of said positively charged regions and a plurality of said negatively charged regions are arranged alternately along said direction.

6. 6. An insulating device according to claim 1, wherein the length of the positively charged region along the direction is 500 nm or more.

7. The positively charged regions are SiO ｘ The insulating device according to any one of claims 1 to 6, wherein x is less than 2.

8. The insulating device according to any one of claims 1 to 6, wherein the insulating film contains silicon and oxygen, and the oxygen concentration in the positively charged region is lower than the oxygen concentration in a region of the insulating film other than the positively charged region.

9. 7. The insulating device according to claim 1, wherein the insulating film comprises silicon and oxygen, and the positively charged regions comprise hafnium and oxygen.

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