JP6012831B2 - Solid-state imaging device - Google Patents

Description

  The present invention relates to a solid-state imaging device, and more particularly to an element isolation structure of a solid-state imaging device.

  Patent Document 1 discloses an element isolation structure between a photoelectric conversion unit and a pixel transistor (active element). Specifically, an element isolation structure having the following characteristics is disclosed. First, the element isolation region is formed of a semiconductor region having a conductivity type opposite to the source region and the drain region of the pixel transistor. Second, an insulating film disposed from the channel region of the pixel transistor to the element isolation region is formed in a flat state without a step. According to Patent Document 1, such an element isolation structure can reduce the area occupied by a pixel transistor.

JP 2009-016810 A

  The present inventor has found the following problems with respect to the element isolation structure described in Patent Document 1. That is, when the element isolation structure described in Patent Document 1 is applied as it is in order to isolate the transfer unit from other elements, there is a problem that the charge transfer efficiency decreases.

  The present invention is based on the above knowledge, and an object thereof is to improve charge transfer efficiency in a solid-state imaging device.

  The solid-state imaging device according to the present invention includes a semiconductor substrate including an active region, a first semiconductor region of a first conductivity type, and a second semiconductor region of a second conductivity type that is a conductivity type different from the first conductivity type. A floating diffusion, an insulator disposed on the semiconductor substrate in contact with the semiconductor substrate, a floating diffusion disposed on the semiconductor substrate via the insulator, and a charge from the first semiconductor region to the floating diffusion. In a solid-state imaging device having a transfer gate electrode for controlling transfer, the first semiconductor region, the second semiconductor region, and the floating diffusion are arranged in the active region, and a part of the first semiconductor region is The part of the first semiconductor region and the second semiconductor region are arranged to overlap with a part of the transfer gate electrode, and the semiconductor substrate and the insulation are The distance from the interface to the position of the partial impurity concentration peak of the first semiconductor region is equal to the impurity concentration peak of the second semiconductor region from the interface. It is different from the distance to the position.

  According to the solid-state imaging device according to the present invention, it is possible to improve the charge transfer efficiency.

1 is a schematic diagram of a planar structure of a solid-state imaging device according to Embodiment 1 of the present invention. 1 is an equivalent circuit diagram of a solid-state imaging device according to Embodiment 1 of the present invention. 1 is a schematic diagram of a cross-sectional structure of a solid-state imaging device according to Embodiment 1 of the present invention. FIG. 3 is an impurity distribution diagram of the solid-state imaging device according to the first embodiment of the present invention. Schematic of the cross-sectional structure of the solid-state imaging device concerning Example 2 of this invention. FIG. 6 is an impurity distribution diagram of a solid-state imaging device according to Embodiment 2 of the present invention. Schematic of the cross-sectional structure of the solid-state imaging device which concerns on Example 3 of this invention. FIG. 6 is an impurity distribution diagram of a solid-state imaging device according to Embodiment 3 of the present invention. Schematic of the planar structure of the solid-state imaging device concerning Example 4 of the present invention. FIG. 6 is an equivalent circuit diagram of a solid-state imaging device according to Embodiment 4 of the present invention. Schematic of the planar structure of the solid-state imaging device concerning Example 5 of the present invention.

  The solid-state imaging device according to the present invention has a semiconductor substrate 1. The semiconductor substrate 1 is a part of a semiconductor material among members constituting the solid-state imaging device. The semiconductor substrate 1 refers to a semiconductor wafer in which a semiconductor region is formed by a known semiconductor manufacturing process, for example. An example of the semiconductor material is silicon. An insulator 2 is disposed on the semiconductor substrate 1 in contact with the semiconductor substrate 1. The insulator 2 is a silicon oxide film, for example. The semiconductor substrate 1 has an active region. The active region is a region in the semiconductor substrate 1 where a semiconductor region constituting an element is disposed. The boundary of the active region is defined by the insulator separator. That is, it can be said that the region where the insulator separating portion is not disposed is the active region. The insulator separation portion is sometimes called a field portion. Specifically, the boundary of the active region is defined by LOCOS (LOCal Oxidation of Silicon) or STI (Shallow Trench Isolation). Alternatively, the entire semiconductor substrate 1 may be an active region. Insulator separation parts such as STI and LOCOS have locally thicker insulators or grooves in the semiconductor substrate. Such an unprocessed region can be referred to as an active region. In the active region, the interface between the semiconductor substrate 1 and the insulator 2 may be substantially flat. Nearly flat means that the interface is not an ideal surface due to, for example, a step due to stacking faults or warpage at the wafer level.

  In addition, the plane in this specification is a plane parallel to the interface between the semiconductor substrate 1 and the insulator 2 in the active region. The depth direction in this specification is a direction perpendicular to the interface between the semiconductor substrate 1 and the insulator 2 in the active region.

  The main part of the present invention will be described below with reference to FIG. FIG. 1 is a schematic plan view of a solid-state imaging device. FIG. 1 shows a plurality of active regions 115a, 115b, and 115c. Specifically, an active region 115a in which a photoelectric conversion unit and an FD are disposed, and active regions 115b and 115c in which a source region and a drain region of a pixel transistor are disposed are illustrated. An N-type semiconductor region 101 is disposed in the active region 115a. For example, the N-type semiconductor region 101 constitutes a part of the photoelectric conversion unit. Examples of the photoelectric conversion unit include a photodiode (hereinafter referred to as PD). Electrons generated by photoelectric conversion are collected in the N-type semiconductor region 101. The N-type semiconductor region 101 may be a region where electrons generated by photoelectric conversion can be accumulated. A floating diffusion (hereinafter referred to as FD) 105 is disposed in the active region 115a. The FD 105 is configured by an N-type semiconductor region. A transfer gate electrode 103 for transferring electrons from the N-type semiconductor region 101 to the FD 105 is disposed on the semiconductor substrate 1 via the insulator 2.

  As shown in FIG. 1, a part of the N-type semiconductor region 101 constituting the PD and a part of the transfer gate electrode 103 overlap each other. In other words, when the N-type semiconductor region 101 and the transfer gate electrode 103 are projected on one plane, a part of the N-type semiconductor region 101 and a part of the transfer gate electrode 103 are projected on the same region on the plane. .

  A P-type semiconductor region 106 is disposed in the active region 115a. A portion of the N-type semiconductor region 101 overlapping the transfer gate electrode 103 and the P-type semiconductor region 106 are arranged adjacent to each other in the planar direction. The planar direction is a direction along the interface between the semiconductor substrate 1 and the insulator 2. Thus, the P-type semiconductor region 106 can function as a potential barrier against electrons in the N-type semiconductor region 101. Alternatively, the P-type semiconductor region 106 may have a function of electrically isolating the N-type semiconductor region 101 from other elements. The other element is another N-type semiconductor region disposed in the active region 115a. For example, the P-type semiconductor region 106 may have a function as element isolation that electrically isolates the N-type semiconductor region 101 and the N-type semiconductor region 102 included in another photoelectric conversion unit. Alternatively, the P-type semiconductor region 106 may have a function of electrically separating the N-type semiconductor region 101 and the conductor embedded in the active region 115a. Thus, when the P-type semiconductor region 106 functions as at least a potential barrier or element isolation with respect to the N-type semiconductor region 101, it can be considered that the P-type semiconductor region 106 is disposed adjacent to the N-type semiconductor region 101. it can. Further, when the P-type semiconductor region 106 forms a PN junction with the N-type semiconductor region 101, it may be considered that the P-type semiconductor region 106 is disposed adjacent to the N-type semiconductor region 101.

  In the present invention, the depth from the interface between the semiconductor substrate 1 and the insulator 2 to the position of the impurity concentration peak in the N-type semiconductor region 101 is such that the impurity in the P-type semiconductor region 106 extends from the interface between the semiconductor substrate 1 and the insulator 2. It is characterized by a difference from the depth to the concentration peak position. 4A and 4B show the impurity distribution along the depth direction in the semiconductor substrate 1. The vertical axis represents the impurity concentration and the horizontal axis represents the depth. The plot of impurity concentration along the depth direction draws a curve. The point at which this curve reaches the maximum is the impurity concentration peak. Here, the reference of the depth (the origin of the horizontal axis) is the interface between the semiconductor substrate 1 and the insulator 2 in the photoelectric conversion unit.

  Next, the effect that the position of the impurity concentration peak of the N-type semiconductor region 101 is different from the position of the impurity concentration peak of the P-type semiconductor region 106 will be described. First, it will be described that the transfer efficiency of charges from the N-type semiconductor region 101 to the FD 105 is improved because a part of the N-type semiconductor region 101 overlaps with the transfer gate electrode 103. Next, since the P-type semiconductor region 106 is disposed adjacent to a portion of the N-type semiconductor region 101 that overlaps the transfer gate electrode 103, the effect of improving the transfer efficiency may be reduced. Explain that there is. Finally, it will be described that the above-described problems are solved and the transfer efficiency is improved by the positional relationship in the depth direction of the impurity concentration peak, which is a characteristic part of the present invention.

  When charges are transferred from the N-type semiconductor region 101 to the FD 105, a predetermined voltage is supplied to the transfer gate electrode 103. As a result, a channel is formed immediately below the transfer gate electrode 103. The predetermined voltage is a voltage necessary to form this channel. Charges move from the N-type semiconductor region 101 to the FD 105 through the channel. In the present invention, a part of the N-type semiconductor region 101 and a part of the transfer gate electrode 103 are overlapped. That is, a part of the N-type semiconductor region 101 is arranged in a region where a channel immediately below the transfer gate electrode 103 is to be formed. This suppresses the generation of a potential barrier in the channel. As a result, transfer efficiency is improved.

  On the other hand, a P-type semiconductor region 106 is formed by adding a P-type impurity (acceptor) to a predetermined region. However, depending on the position control accuracy of the semiconductor process to which the P-type impurity is added, the P-type impurity may be added to a region other than the predetermined region. Alternatively, P-type impurities can diffuse into a region other than the predetermined region during the heat treatment after ion implantation. For this reason, when the P-type semiconductor region 106 is disposed adjacent to the N-type semiconductor region 101, a P-type impurity may be added to the N-type semiconductor region 101. N-type impurities (donors) in the N-type semiconductor region 101 are compensated by such P-type impurities.

  In particular, when the position of the impurity concentration peak of the N-type semiconductor region 101 and the impurity concentration peak of the P-type semiconductor region 106 are the same depth, a portion having a relatively high impurity concentration in the P-type semiconductor region 106 is the N-type semiconductor. It is arranged near the area 106. Therefore, the N-type impurities in the N-type semiconductor region 101 are compensated by a large number of P-type impurities. As a result, the impurity concentration of the N-type semiconductor region 101 may be significantly reduced. Alternatively, a region that should be an N-type semiconductor region may be an intrinsic semiconductor region or a P-type semiconductor region. In this case, the area of the N-type semiconductor region 101 may be significantly reduced.

  Furthermore, among the N-type semiconductor region 101, the impurity concentration or area of a region having a relatively high impurity concentration including the portion where the impurity concentration peak is arranged tends to be small. A region having a relatively high impurity concentration in the N-type semiconductor region 101 contributes predominantly to the above-described effect of improving transfer efficiency. Therefore, if the impurity concentration or area of such a region is small, the effect of improving transfer efficiency tends to be small.

  Thus, if the impurity concentration of the portion of the N-type semiconductor region 101 that overlaps with the transfer gate electrode 103 is reduced or the area thereof is reduced, the transfer efficiency may be reduced. This is because, firstly, the effect of improving the transfer efficiency described above is reduced. Alternatively, secondly, the effective channel width is narrowed by reducing the length in the channel width direction of the portion of the N-type semiconductor region 101 that overlaps with the transfer gate electrode 103.

  If the impurity concentration or area of the portion of the N-type semiconductor region 101 that does not overlap the transfer gate electrode 103 is reduced, for example, the sensitivity and the amount of saturated charge may be reduced. However, since the area of the N-type semiconductor region 101 is sufficiently large, the influence is considered to be negligible. On the other hand, a part of the N-type semiconductor region 101 that overlaps with the transfer gate electrode 103 has a small area. Therefore, even if the absolute amount in which the impurity concentration or the area decreases is the same, the relative ratio increases. Thus, the present inventor has found that a reduction in transfer efficiency due to a decrease in the concentration or area of a part of the impurity disposed overlapping the transfer gate electrode 103 of the N-type semiconductor region 101 is a problem to be solved. .

  In the present invention, the depth of the impurity concentration peak of the N-type semiconductor region 101 is different from the position of the impurity concentration peak of the P-type semiconductor region 106. For this reason, it is possible to improve the above-mentioned problem.

  According to the present invention, the impurity concentration peak of the N-type semiconductor region 101 and the impurity concentration peak of the P-type semiconductor region 106 are arranged at different depths. Therefore, even if the N-type semiconductor region 101 and the P-type semiconductor region 106 are disposed adjacent to each other on the plane, the portions with high impurity concentrations are disposed at a predetermined distance in the depth direction. This reduces the number of N-type impurities that are compensated by the P-type impurities in the P-type semiconductor region 106 among the N-type impurities in the N-type semiconductor region 101. Therefore, the impurity concentration or area of the N-type semiconductor region 101 is difficult to decrease, and as a result, an effect of improving transfer efficiency due to a part of the N-type semiconductor region 101 overlapping with a part of the transfer gate electrode 103 is obtained. Get higher.

  Note that a semiconductor region having an impurity concentration peak can be formed by various methods. One technique is ion implantation. When the semiconductor region is formed by ion implantation, the semiconductor region has an impurity concentration peak at a predetermined depth. Thereafter, heat treatment may be performed under the condition that the impurity concentration peak remains. Even when the semiconductor region is formed using ion implantation, the semiconductor region formed by ion implantation with energy such that the impurity concentration peak is located in the insulator 2 stacked on the semiconductor substrate 1 is However, the semiconductor region does not necessarily have an impurity concentration peak.

  Further, the present invention is more effective when applied to a configuration in which the area of the FD 105 in a plane is smaller than the area of the N-type semiconductor region 101 in the plane. The reason is as follows. When the FD area is smaller than the PD area, the channel width is narrower than the PD channel width. In addition, a shorter channel length is advantageous in terms of transfer efficiency. Therefore, the channel area is often smaller than the PD area. Therefore, a part of the N-type semiconductor region 101 arranged so as to overlap the transfer gate electrode 103 has a very small area compared to the area of the remaining part of the N-type semiconductor region 101. Therefore, when the present invention is applied to such a configuration, a higher effect can be obtained.

  Furthermore, since the area of the FD 105 in the plane is smaller than the area of the N-type semiconductor region 101 in the plane, the effects of improving sensitivity, saturation charge, or charge voltage conversion efficiency can be obtained. The reason is that PD having a large area is more advantageous in order to increase sensitivity and saturation charge. Second, in order to increase the charge-voltage conversion efficiency, it is preferable that the capacity of the FD is small, and for that purpose, the FD having a small area is more advantageous. Here, the area of the PD on a plane means the area of a region where the PD on the plane is projected when the PD is projected onto one plane. The area of the FD 105 on a plane means the area of a region where the FD 105 on the plane is projected when the FD 105 is projected on one plane. In the following description, the area in a plane is simply referred to as “area” unless otherwise specified.

  In the above description, the configuration in which electrons are used as signal charges has been illustrated, but holes can also be used as signal charges. When electrons are used as signal charges, the first conductivity type is N-type and the second conductivity type is P-type. When holes are used as signal charges, the conductivity type of each semiconductor region may be set to the opposite conductivity type when the signal charges are electrons. That is, the first conductivity type is P-type and the second conductivity type is N-type.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic plan view of a first embodiment of a solid-state imaging device according to the present invention.

  Reference numerals 101 and 102 denote N-type semiconductor regions constituting the photoelectric conversion unit. Each of them forms a PD by forming a PN junction with a P-type semiconductor region disposed deep in the semiconductor substrate. This P-type semiconductor region is, for example, a P-type well or a P-type buried layer. Light incident on the photoelectric conversion unit is converted into electric charge. Charges generated by photoelectric conversion are accumulated in the N-type semiconductor regions 101 and 102.

  Reference numerals 103 and 104 denote transfer gate electrodes. Reference numeral 105 denotes an FD. The charge in the N-type semiconductor region 101 is transferred to the FD 105 by the transfer gate electrode 103. The charge in the N-type semiconductor region 102 is transferred to the FD 105 by the transfer gate electrode 104. The FD 105 functions as an input unit of an amplification unit described later. Specifically, the FD 105 converts the charge transferred to the FD 105 into a voltage corresponding to the amount of charge. In this embodiment, the charges of the two N-type semiconductor regions 101 and 102 are transferred to the FD 105 which is a common node. However, in each photoelectric conversion unit, the charge of the N-type semiconductor region 101 is transferred to the first FD, and the charge of the N-type semiconductor region 102 is transferred to a second FD different from the first FD. On the other hand, the FD may be a separate node.

  A P-type semiconductor region 106 is disposed between the N-type semiconductor region 101 and the N-type semiconductor region 102. The P-type semiconductor region 106 electrically isolates the N-type semiconductor region 101 and the N-type semiconductor region 102.

  The P-type semiconductor region 107 is a surface region for making the PD a buried photodiode. The P-type semiconductor region 107 is disposed at a shallower position on the semiconductor substrate than the N-type semiconductor regions 101 and 102. The P-type semiconductor region 107 is preferably arranged so as to overlap the entire surface of the N-type semiconductor region 101. Of course, a configuration in which the P-type semiconductor region 107 is disposed so as to overlap only a part of the N-type semiconductor region 101 may be employed. Further, the P-type semiconductor region 107 may be disposed so as to overlap with part or all of the P-type semiconductor region 106. The P-type semiconductor region 107 is preferably electrically connected to the P-type semiconductor region 106.

  Reference numeral 108 denotes a gate electrode of the reset transistor. Reference numerals 109 and 110 denote a source region and a drain region of the reset transistor, respectively. The source region 109 of the reset transistor and the FD 105 are electrically connected. Reference numeral 111 denotes a gate electrode of the amplification transistor. Reference numerals 112 and 113 denote a source region and a drain region of the amplification transistor, respectively. The gate electrode 111 of the amplification transistor and the FD 105 are electrically connected.

  Reference numeral 114 denotes an insulator separator. The insulator separator 114 is, for example, an STI. The region where the boundary is defined by the insulator separator 114 is the active region. Specifically, in FIG. 1, a region surrounded by solid lines 115a to 115c is an active region.

  As shown in FIG. 1, a part of the N-type semiconductor region 101 is disposed so as to overlap the transfer gate electrode 103. Then, the P-type semiconductor region 106 is disposed in the active region 115 a adjacent to a part of the N-type semiconductor region that is disposed so as to overlap the transfer gate electrode 103.

  Of the portion overlapping the transfer gate electrode 103 in the active region 115a, the P-type semiconductor region is disposed in a region where neither the N-type semiconductor region 101 nor the P-type semiconductor region 106 is disposed. This P-type semiconductor region is, for example, a P-type well. Alternatively, channel doping may be performed to form a threshold adjustment region for transistor threshold adjustment.

  FIG. 2 is an equivalent circuit diagram of a pixel in this embodiment. Reference numeral 201 denotes a first photoelectric conversion unit, and 202 denotes a second photoelectric conversion unit. The first photoelectric conversion unit 201 includes the N-type semiconductor region 101 of FIG. The second photoelectric conversion unit 202 includes the N-type semiconductor region 102 of FIG.

  Reference numeral 203 denotes a first transfer transistor, and 204 denotes a second transfer transistor. The gate of the first transfer transistor 203 includes the transfer gate electrode 103 of FIG. The N-type semiconductor region 101 in FIG. 1 corresponds to the source of the first transfer transistor 203. The FD 105 in FIG. 1 corresponds to the drain of the first transfer transistor 203. The transfer gate electrode 104, the N-type semiconductor region 102, and the FD 105 in FIG. 1 correspond to the gate, source, and drain of the second transfer transistor 204, respectively.

  Reference numeral 206 denotes a reset transistor. Reference numeral 207 denotes an amplification transistor. Reference numeral 205 denotes an input node of the amplification transistor 207. The FD 105 in FIG. 1 corresponds to the input node 205 of the amplification transistor 207. That is, in this embodiment, the FD 105 functions as an input unit of the amplification transistor.

  Reference numeral 208 denotes a power source. The power source 208 is electrically connected to the drain of the reset transistor 206 and the drain of the amplification transistor 207. The source of the amplification transistor 207 is connected to the output line 209.

  With the circuit configuration as described above, a signal corresponding to the light incident on the photoelectric conversion unit is output to the output line 209. This operation will be briefly described. First, when the reset transistor 206 is turned on, the input node 205 is reset to the power supply voltage. Next, when the transfer transistor 203 is turned on, the charge accumulated in the first photoelectric conversion unit 201 is transferred to the input node 205. The charge transferred to the input node 205 is converted into a voltage. That is, the voltage at the input node 205 changes by a voltage corresponding to the amount of charge transferred from the power supply voltage from the voltage at the time of reset. The amplification transistor outputs a voltage according to the voltage of the input node to the output line 209. On / off of the first transfer transistor 203, the second transfer transistor 204, and the reset transistor 206 is controlled by a voltage supplied to each gate.

  Next, the structure of the cross section of this example and the distribution of impurities along the depth direction will be described. 3A, 3B, and 3C are schematic views of cross sections taken along the straight line AB, the straight line CD, and the straight line EF of FIG. 1, respectively. Parts corresponding to those in FIG. 1 are denoted by the same reference numerals.

  FIG. 4A shows the impurity distribution along the broken line P11 and the broken line P12 in FIG. FIG. 4B shows the impurity distribution along the broken lines P13 and P14 in FIG. 4A and 4B, the vertical axis represents the impurity concentration, and the horizontal axis represents the depth from the interface between the semiconductor substrate and the insulator 2.

  FIG. 3A shows a cross section of two photoelectric conversion units. The P-type semiconductor region 106 is arranged extending to a deeper position of the semiconductor substrate than the N-type semiconductor regions 102 and 103. Therefore, the N-type semiconductor regions 101 and 102 are electrically isolated by the element isolation unit 106 even at a deep position from the interface. A P-type semiconductor region 107 is disposed at a position shallower than the N-type semiconductor regions 101 and 102 and the P-type semiconductor region 106. Reference numeral 302 denotes an interface between the semiconductor substrate 1 and the insulator 2. The insulator 2 is disposed on the semiconductor substrate 1 so as to be in contact with the semiconductor substrate 1. By electrically extending the P-type semiconductor region 107 so as to overlap with the element isolation layer 106, electrical isolation between the N-type semiconductor region 101 and the N-type semiconductor region 102 can be more effectively performed. Is possible.

  Reference numeral 301 denotes a P-type semiconductor region. The P-type semiconductor region 301 forms a PN junction with the N-type semiconductor regions 101 and 102. The P-type semiconductor region 301 is a P-type well disposed on an N-type semiconductor substrate, for example. The P-type well may be constituted by a plurality of P-type semiconductor regions arranged at different depths. Alternatively, the P-type semiconductor region 301 may be a P-type semiconductor substrate. That is, the photoelectric conversion unit is configured by arranging the N-type semiconductor region at a predetermined position of the P-type semiconductor substrate, and the N-type semiconductor region is not arranged and remains in the original P-type semiconductor substrate. The region may be a P-type semiconductor region 301.

  FIG. 4A shows the impurity distribution along the broken line P11 and the broken line P12 in FIG. A broken line P11 indicates a depth direction in the photoelectric conversion unit. A broken line P12 indicates a depth direction in the region where the P-type semiconductor region 106 is disposed. In the photoelectric conversion portion, impurities contained in the P-type semiconductor region 107, impurities contained in the N-type semiconductor region 102, and impurities contained in the P-type semiconductor region 301 are arranged in order from the shallowest. In the region where the P-type semiconductor region 106 is arranged, an impurity contained in the P-type semiconductor region 107, an impurity contained in the P-type semiconductor region 106, and an impurity contained in the P-type semiconductor region 301 are arranged in order from the shallowest. . Thus, in the figure showing the impurity distribution, the impurity distribution in the N-type semiconductor region is represented by “n”, and the impurity distribution in the P-type semiconductor region is represented by “p”. . The same applies to the following figures.

  As shown in FIG. 4A, the position of the impurity concentration peak in the N-type semiconductor region 101 is different in depth from the position of the impurity concentration peak in the P-type semiconductor region 106. In this embodiment, the position of the impurity concentration peak of the N-type semiconductor region 101 is shallower than the position of the impurity concentration peak of the P-type semiconductor region 106.

  Although not illustrated, the position of the impurity concentration peak of the N-type semiconductor region 102 is different in depth from the position of the impurity concentration peak of the P-type semiconductor region 106. In this embodiment, the position of the impurity concentration peak in the N-type semiconductor region 102 is shallower than the position of the impurity concentration peak in the P-type semiconductor region 106.

  3B and 3C are schematic views of a cross section including the transfer gate electrode 103. FIG. FIG. 3B is a schematic view of a cross section perpendicular to the charge transfer direction from the N-type semiconductor region 101 to the FD 105. FIG. 3C shows a schematic view of a cross section including the charge transfer direction.

  3B and 3C, the transfer gate electrode 103 is disposed on the semiconductor substrate 1 via an insulator (not shown). As shown in FIGS. 3B and 3C, a part of the N-type semiconductor region 101 is arranged so as to overlap the transfer gate electrode 103. As shown in FIG. 3B, a P-type semiconductor region 106 is disposed in a region adjacent to a part of the N-type semiconductor region 101 disposed so as to overlap with the transfer gate electrode 103. Note that an insulator separating portion 104 is disposed on the opposite side to the P-type semiconductor region 106. Further, as shown in FIG. 3B, a part of the transfer gate electrode 103 may overlap with the P-type semiconductor region 106.

  As shown in FIGS. 3B and 3C, a part of the N-type semiconductor region 101 that overlaps with the transfer gate electrode 103 does not overlap with the P-type semiconductor region 107. In other words, the N-type semiconductor region 101 extends closer to the FD 105 along the charge transfer direction than the P-type semiconductor region 107. According to such a configuration, the charge transfer efficiency can be improved.

  Such a structure can be manufactured by the following method. For example, first, the transfer gate electrode 103 is formed. Thereafter, the N-type semiconductor region 101 is formed by inclining the impurity in the direction of getting under the transfer gate electrode 103 to form the N-type semiconductor region 101, and conversely, injecting the impurity in the direction away from the transfer gate electrode 103. Thus, the P-type semiconductor region 107 is formed. As another method, first, the N-type semiconductor region 101 is formed. Thereafter, the transfer gate electrode 103 is formed so as to overlap with the N-type semiconductor region 101. Thereafter, a P-type semiconductor region 107 is formed using the transfer gate electrode 103 as a mask.

  FIG. 4B shows the impurity distribution along the broken lines P13 and P14 in FIG. A broken line P13 indicates the depth direction in the region where the N-type semiconductor region 101 and the transfer gate electrode 103 overlap. A broken line P14 indicates a depth direction in the P-type semiconductor region 106 disposed adjacent to a part of the N-type semiconductor region 101 disposed so as to overlap the transfer gate electrode 103. In the region where the N-type semiconductor region 101 and the transfer gate electrode 103 overlap, impurities contained in the N-type semiconductor region 101 and impurities contained in the P-type semiconductor region 301 are arranged in order from the shallowest. In the region where the P-type semiconductor region 106 is arranged, an impurity contained in the P-type semiconductor region 107, an impurity contained in the P-type semiconductor region 106, and an impurity contained in the P-type semiconductor region 301 are arranged in order from the shallowest. .

  As shown in FIG. 4B, the position of the impurity concentration peak of a part of the N-type semiconductor region 101 arranged so as to overlap with the transfer gate electrode 103 is different from the position of the impurity concentration peak of the P-type semiconductor region 106. That's it. In this embodiment, a part of the impurity concentration peak of the N-type semiconductor region 101 is arranged at a position shallower than the impurity concentration peak of the P-type semiconductor region 106.

  Although not shown, the position of the impurity concentration peak of a part of the N-type semiconductor region 102 that overlaps with the transfer gate electrode 104 has a depth different from the position of the impurity concentration peak of the P-type semiconductor region 106. It is. In this embodiment, a part of the impurity concentration peak of the N-type semiconductor region 102 is disposed at a position shallower than the impurity concentration peak of the P-type semiconductor region 106.

  The effect of the present invention can be obtained if the position of a part of the impurity concentration peak of the N-type semiconductor region 102 and the position of the impurity concentration peak of the P-type semiconductor region 106 are slightly different. The depth from the interface 302 to the position of a part of the impurity concentration peak of the N-type semiconductor region 102 is different from the depth from the interface 302 to the position of the impurity concentration peak of the P-type semiconductor region 106 by 50 angstroms or more. Is preferred. In addition, when the semiconductor region is formed by ion implantation, it is preferable that the difference in depth is greater than one tenth of the standard deviation of the penetration depth. The standard deviation is the distance from the average ion penetration depth to the depth at which the impurity concentration is half the impurity concentration at the average penetration depth. That is, the distance from the position of the impurity concentration peak to the position where the impurity concentration is half the value of the impurity concentration peak is the standard deviation.

  In this embodiment, a P-type semiconductor region having an impurity concentration peak having the same depth as the impurity concentration peak of the N-type semiconductor region 101 may be disposed adjacent to the N-type semiconductor region 101. For example, this is a case where the impurity concentration of the P-type semiconductor region is sufficiently lower than the impurity concentration of the N-type semiconductor region 101 or the P-type semiconductor region 106. For example, when the impurity concentration is 1/10 or less. When the impurity concentration is 1/10 or less, the influence on the impurity concentration of the N-type semiconductor region 101 and the P-type semiconductor region 106 is about 10% at most. Therefore, the effect may be negligible.

  Considering that incident light is photoelectrically converted in the substrate, if the P-type semiconductor region 107 is formed deeply, signal charges disappear due to recombination, resulting in a decrease in sensitivity. It is desirable that the depth to be formed is shallower. Specifically, the position of the impurity concentration peak of the P-type semiconductor region 107 is preferably a depth within 0.10 micrometers from the interface 302. The impurity concentration peak of the impurity implanted to form the P-type semiconductor region 107 may be located in the insulator stacked on the semiconductor substrate 1. In such a case, there is no impurity concentration peak inside the P-type semiconductor region 107. In order to reduce the segregation and pileup of impurities at the interface 302, when electrons are used as signal charges, the P-type semiconductor region 107 is preferably formed of boron or a boron compound. When holes are used as signal charges, the conductivity types are reversed. That is, the N-type semiconductor region 107 is preferably formed of arsenic or an arsenic compound.

  In addition, when a part of the N-type semiconductor region 101 overlapping with the transfer gate electrode 103 is arranged deeply, there is a possibility that the voltage required for charge transfer becomes high. Therefore, the position of a part of the impurity concentration peak of the N-type semiconductor region 101 arranged so as to overlap with the transfer gate electrode 103 is deeper than the interface 302 by 0.00 micrometers and shallower than the interface 302 by 0.30 micrometers. It is desirable. The depth from the interface 302 to the position of a part of the impurity concentration peak in the N-type semiconductor region 101 is more preferably in the range of 0.10 to 0.20 micrometers. In consideration of impurity diffusion, when electrons are used as signal charges, the N-type semiconductor region 101 is preferably formed of arsenic or an arsenic compound. When holes are used as signal charges, the conductivity types are reversed. That is, the P-type semiconductor region 101 is preferably formed of boron or a boron compound.

  The depth from the interface 302 to the position of the impurity concentration peak of the P-type semiconductor region 106 is preferably in the range of 0.20 to 0.30 micrometers. Furthermore, the depth from the interface 302 to the position of the impurity concentration peak of the P-type semiconductor region 106 is more preferably in the range of 0.22 to 0.25 micrometers. In consideration of impurity diffusion, when electrons are used as signal charges, the P-type semiconductor region 106 is preferably formed of boron or a boron compound. When holes are used as signal charges, the element isolation layer 106 is preferably formed of arsenic or an arsenic compound.

  Thus, in this embodiment, the position of a part of the impurity concentration peak of the N-type semiconductor region 101 arranged so as to overlap the transfer gate electrode 103 is shallower than the position of the impurity concentration peak of the P-type semiconductor region 106. According to such a configuration, it is possible to perform electrical separation while reducing the voltage required for charge transfer.

  As described above, in this embodiment, the position of the impurity concentration peak of the N-type semiconductor region 101 and the position of the impurity concentration peak of the P-type semiconductor region 106 have different depths. According to such a configuration, it is possible to suppress a decrease in the impurity concentration of the portion overlapping the transfer gate electrode 103 in the N-type semiconductor region 101. As a result, the charge transfer efficiency from the photoelectric conversion unit to the FD 105 can be improved.

  In this embodiment, the charges of a plurality of photoelectric conversion units are transferred to a common FD. At this time, charges are transferred in a direction (a direction indicated by a straight line EF in FIG. 1) different from a direction in which a plurality of photoelectric conversion units are arranged (a direction indicated by a straight line AB in FIG. 1). In such a configuration, the plurality of photoelectric conversion units are arranged close to each other. In order to separate the two photoelectric conversion portions arranged close to each other, it is desirable that the impurity concentration of the P-type semiconductor region 106 is higher. On the other hand, when the impurity concentration of the P-type semiconductor region 106 is increased, the effective width of the transfer channel is narrowed by the diffusion of impurities. That is, ensuring the electrical separation performance and securing the width of the transfer channel are in a trade-off relationship. Therefore, the problem that the charge transfer efficiency is lowered becomes more prominent. Therefore, a more remarkable effect can be obtained by applying the present invention in a configuration in which the charges of a plurality of photoelectric conversion units are transferred to a common FD as in this embodiment.

  A second embodiment according to the present invention will be described. The planar structure, equivalent circuit, and operation of this embodiment are the same as those of the first embodiment. The difference from the first embodiment is that a plurality of N-type semiconductor regions arranged at different depths are included in one photoelectric conversion unit. This point will be described with reference to the drawings.

  The planar structure of this embodiment is shown in FIG. FIGS. 5A, 5B, and 5C are schematic views of cross sections taken along the straight line AB, the straight line CD, and the straight line EF, respectively, of FIG. FIG. 6A shows the impurity distribution along the broken line P21 and the broken line P22 in FIG. FIG. 6B shows the impurity distribution along the broken lines P23 and P24 in FIG. 6A and 6B, the vertical axis represents the impurity concentration, and the horizontal axis represents the depth from the interface between the semiconductor substrate 1 and the insulator. Parts having the same functions as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIGS. 5A to 5C, in this embodiment, the N-type semiconductor region 501 is arranged at a position deeper from the interface 302 than the N-type semiconductor region 101. When viewed in a plan view, part or all of the N-type semiconductor region 501 overlaps with the N-type semiconductor region 101. The N-type semiconductor regions 101 and 501 are included in one photoelectric conversion unit (first photoelectric conversion unit 201 in FIG. 2). Further, as shown in FIG. 5A, the N-type semiconductor region 502 is arranged at a position deeper from the interface 302 than the N-type semiconductor region 102. When viewed in a plan view, part or all of the N-type semiconductor region 502 overlaps with the N-type semiconductor region 102. The N-type semiconductor regions 102 and 502 are included in one photoelectric conversion unit (second photoelectric conversion unit 202 in FIG. 2).

  FIG. 6A shows the impurity distribution along the depth direction (broken line P21) in the photoelectric conversion unit. Since the N-type semiconductor region 101 and the N-type semiconductor region 501 arranged at different depths overlap each other, two impurity concentration peaks corresponding to the two N-type semiconductor regions are arranged. That is, the impurity concentration peak of the N-type semiconductor region 101 and the impurity concentration peak of the N-type semiconductor region 201. The position of the impurity concentration peak of the N-type semiconductor region 101 is shallower than the position of the impurity concentration peak of the N-type semiconductor region 501. 6A shows the impurity distribution along the depth direction (broken line P22) in the P-type semiconductor region 106. FIG. As shown in FIG. 6A, the position of the impurity concentration peak of the P-type semiconductor region 106 is different from the position of the impurity concentration peak of the N-type semiconductor regions 101 and 501.

  FIG. 6B shows the distribution of impurities along the depth direction (broken line P23) in a part of the N-type semiconductor region 101 arranged so as to overlap the transfer gate electrode 103. FIG. FIG. 6B shows the impurity distribution along the depth direction (broken line P24) in the P-type semiconductor region 106 disposed adjacent to a part of the N-type semiconductor region 101. FIG. As shown in FIG. 6B, the position of the impurity concentration peak of the P-type semiconductor region 106 is different from the position of the impurity concentration peak of the N-type semiconductor regions 101 and 501. In this embodiment, the impurity concentration peak of the N-type semiconductor region 101, the impurity concentration peak of the P-type semiconductor region 106, and the impurity concentration peak of the N-type semiconductor region 501 are arranged in order from the side closer to the interface 302.

  In this embodiment, the depth from the interface 302 to the position of the impurity concentration peak in the N-type semiconductor region 101 is preferably in the range of 0.10 to 0.20 micrometers. The depth from the interface 302 to the position of the impurity concentration peak of the P-type semiconductor region 106 is preferably in the range of 0.20 to 0.25 micrometers. The depth from the interface 302 to the position of the impurity concentration peak of the N-type semiconductor region 501 is preferably in the range of 0.25 to 0.35 micrometers. The depth from the interface 302 to the position of the impurity concentration peak of the P-type semiconductor region 107 is preferably in the range of 0.00 to 0.10 micrometers.

  As described above, since a plurality of N-type semiconductor regions having different depths are included in one photoelectric conversion unit, it is easy to dispose the N-type semiconductor region at a deeper position. This is because a plurality of N-type semiconductor regions having different depths can be easily formed by a plurality of ion implantations with different implantation energies. By arranging the N-type semiconductor region at a deep position, it is possible to accumulate charges generated at a deep position on the semiconductor substrate 1. As a result, it is possible to improve sensitivity.

  As shown in FIG. 5C, in this embodiment, the N-type semiconductor region 101 extends to the FD 105 along the charge transfer direction rather than the N-type semiconductor region 501. Such a configuration is advantageous when the N-type semiconductor regions 101 and 501 are formed after the transfer gate electrode 103 is formed. When forming the shallow N-type semiconductor region 101, the voltage necessary for charge transfer from the N-type semiconductor region 101 to the FD 105 is obtained by performing ion implantation with an inclination in the direction of entering the transfer gate electrode 103. It can be lowered. At this time, by increasing the inclination, the shadowing effect by the photoresist and the transfer gate electrode 103 is increased, and the amount of implanted impurities is reduced. As a result, the total impurity amount in the N-type semiconductor region 101 is reduced. In order to compensate for this, when the deep N-type semiconductor region 501 is formed, the angle of inclination is made smaller or vertical than when the N-type semiconductor region 101 is formed. This can reduce the shadowing effect and increase the amount of impurities in the photoelectric conversion unit. As a result, it is possible to keep the voltage required for charge transfer low without reducing the amount of accumulated charge.

  Further, the N-type semiconductor region 101 may be formed by ion implantation of arsenic or an arsenic compound, and the N-type semiconductor region 501 may be formed by ion implantation of phosphorus or a phosphorus compound. Since phosphorus is lighter than arsenic, impurities can be implanted deeper. On the other hand, since arsenic is heavier than phosphorus, there is an advantage that it is difficult to diffuse. Of course, both the N-type semiconductor region 101 and the N-type semiconductor region 501 may be formed by ion implantation of arsenic or an arsenic compound.

  A third embodiment according to the present invention will be described. The planar structure, equivalent circuit, and operation of this embodiment are the same as those of the first and second embodiments. The difference from Example 1 and Example 2 is that a plurality of P-type semiconductor regions having different depths are arranged adjacent to the N-type semiconductor region included in the photoelectric conversion unit. This point will be described with reference to the drawings.

  The planar structure of this embodiment is shown in FIG. FIGS. 7A and 7B are schematic views of cross sections taken along the straight line AB and the straight line CD in FIG. 1, respectively. FIG. 8A shows the impurity distribution along the broken lines P31 and P32 in FIG. FIG. 8B shows the impurity distribution along the broken lines P33 and P34 in FIG. 8A and 8B, the vertical axis represents the impurity concentration, and the horizontal axis represents the depth from the interface between the semiconductor substrate 1 and the insulator. Parts having the same functions as those in the first embodiment or the second embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 7A, in this embodiment, a P-type semiconductor region 106 and a P-type semiconductor region 701 are arranged adjacent to the N-type semiconductor region 101. Both the P-type semiconductor region 106 and the P-type semiconductor region 701 are disposed in the active region 115. Further, as shown in FIG. 7B, a P-type semiconductor region 106 and a P-type semiconductor region 701 are disposed adjacent to a part of the N-type semiconductor region 101 disposed so as to overlap the transfer gate electrode 103. The P-type semiconductor region 701 is disposed deeper from the interface 302 than the P-type semiconductor region 106. When viewed in a plan view, part or all of the P-type semiconductor region 701 overlaps with the P-type semiconductor region 106. The P-type semiconductor region 701 electrically isolates the N-type semiconductor region 101 from other elements. In FIG. 7A, the P-type semiconductor region 701 electrically isolates the N-type semiconductor region 101 and the N-type semiconductor region 102. Thus, in this embodiment, in order to electrically isolate the N-type semiconductor region 101 included in the photoelectric conversion unit from other elements, a plurality of P-type semiconductor regions having different depths are formed in the N-type semiconductor region 101. It is arranged adjacent to.

  In FIG. 8A, the impurity distribution along the depth direction (broken line P31) in the photoelectric conversion unit is the same as that in the second embodiment. The distribution of impurities along the depth direction (broken line P32) in the P-type semiconductor region 106 has an impurity concentration peak in the P-type semiconductor region 106 and an impurity concentration peak in the P-type semiconductor region 701. The positions of the impurity concentration peaks of the P-type semiconductor region 106 and the P-type semiconductor region 701 are both different in depth from the positions of the impurity concentration peaks of the N-type semiconductor region 101.

  In FIG. 8B, the distribution of impurities along the depth direction (broken line P33) in a part of the N-type semiconductor region 101 arranged so as to overlap the transfer gate electrode 103 is the same as that in the second embodiment. The distribution of impurities along the depth direction (broken line P32) in the P-type semiconductor region 106 has an impurity concentration peak in the P-type semiconductor region 106 and an impurity concentration peak in the P-type semiconductor region 701. The positions of the impurity concentration peaks of the P-type semiconductor region 106 and the P-type semiconductor region 701 are both different in depth from the positions of the impurity concentration peaks of the N-type semiconductor region 101. In this embodiment, the impurity concentration peak of the N-type semiconductor region 101, the impurity concentration peak of the P-type semiconductor region 106, the impurity concentration peak of the N-type semiconductor region 501, and the impurity concentration peak of the P-type semiconductor region 701 in order from the shallowest. Is arranged. The depths of the impurity concentration peaks of these four semiconductor regions are all different depths.

  In this embodiment, the depth from the interface 302 to the position of the impurity concentration peak in the N-type semiconductor region 101 is preferably in the range of 0.10 to 0.20 micrometers. The depth from the interface 302 to the position of the impurity concentration peak of the P-type semiconductor region 106 is preferably in the range of 0.20 to 0.25 micrometers. The depth from the interface 302 to the position of the impurity concentration peak of the N-type semiconductor region 501 is preferably in the range of 0.25 to 0.35 micrometers. The depth from the interface 302 to the position of the impurity concentration peak of the P-type semiconductor region 701 is preferably in the range of 0.35 to 0.50 micrometers. The depth from the interface 302 to the position of the impurity concentration peak of the P-type semiconductor region 107 is preferably in the range of 0.00 to 0.10 micrometers.

  As described above, in this embodiment, the P-type semiconductor region 106 and the P-type semiconductor region 701 are disposed adjacent to the N-type semiconductor region 101. The positions of the impurity concentration peaks of the P-type semiconductor region 106 and the P-type semiconductor region 701 are both different in depth from the positions of the impurity concentration peaks of the N-type semiconductor region 101. According to such a configuration, in addition to the effect of the second embodiment, there is an advantage that it becomes easy to arrange the P-type semiconductor region to a deeper position.

  In this embodiment, the impurity concentration peak of the P-type semiconductor region 701 may be disposed at a position shallower than the impurity concentration peak of the N-type semiconductor region 101. The impurity concentration peak of the P-type semiconductor region 106, the impurity concentration peak of the N-type semiconductor region 101, the impurity concentration peak of the P-type semiconductor region 701, and the impurity concentration peak of the N-type semiconductor region 501 are arranged in order from the shallowest. It may be configured. According to such a configuration, it is possible to improve the performance of electrical separation. When a voltage is applied to the transfer gate electrode 103 or other gate electrodes, the potential in a region near the interface 302 changes greatly due to the electric field effect. For this reason, the P-type semiconductor region 106 having a function of electrical isolation is disposed in a region close to the interface, whereby the electrical isolation performance can be improved.

  A fourth embodiment according to the present invention will be described. FIG. 9 is a schematic view of the planar structure of the present embodiment. Portions having functions similar to those of the first to third embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.

This embodiment is characterized in that the charges of the four photoelectric conversion units are transferred to the common FD 105. In FIG. 9, reference numeral 901 denotes an N-type semiconductor region included in the first photoelectric conversion unit. Reference numeral 902 denotes an N-type semiconductor region included in the second photoelectric conversion unit. Reference numeral 903 denotes an N-type semiconductor region included in the third photoelectric conversion unit. Reference numeral 904 denotes an N-type semiconductor region included in the fourth photoelectric conversion unit.
The four N-type semiconductor regions 901 to 904 accumulate charges generated in the first to fourth photoelectric conversion units, respectively. Transfer gate electrodes 905 to 908 are arranged corresponding to the four N-type semiconductor regions 901 to 904, respectively. The charges accumulated in the four N-type semiconductor regions 901 to 904 are transferred to the common FD 105 by the transfer gate electrodes 905 to 908.

  In this embodiment, a part of the N-type semiconductor region 901 is arranged so as to overlap with the corresponding transfer gate electrode 905. Similarly, a part of each N-type semiconductor region 902 to 904 is arranged so as to overlap with the corresponding transfer gate electrodes 906 to 908. Then, the P-type semiconductor region 106 is disposed in the active region 115 adjacent to a part of the transfer gate electrode that overlaps with the transfer gate electrode.

  The distribution of impurities along the depth direction in the region where the N-type semiconductor regions 901 to 904 are arranged is the same as the distribution of impurities in the region where the N-type semiconductor region 101 of Examples 1 to 3 is arranged. Therefore, the position of each impurity concentration peak in the N-type semiconductor regions 901 to 904 is different in depth from the position of the impurity concentration peak in the P-type semiconductor region 106.

  FIG. 10 is an equivalent circuit of this embodiment. Reference numeral 1001 denotes a first photoelectric conversion unit, 1002 denotes a second photoelectric conversion unit, 1003 denotes a third photoelectric conversion unit, and 1004 denotes a fourth photoelectric conversion unit. Reference numeral 1005 denotes a first transfer transistor, 1006 denotes a second transfer transistor, 1007 denotes a third transfer transistor, and 1008 denotes a fourth transfer transistor. The first to fourth transfer transistors are controlled on and off independently of each other.

  As shown in FIG. 10, in this embodiment, four photoelectric conversion units share one amplification transistor 207. According to such a configuration, in addition to the effects of the first to third embodiments, the area of the photoelectric conversion unit can be further increased.

  A fifth embodiment according to the present invention will be described. FIG. 11 is a schematic view of the planar structure of the present embodiment. Parts having the same functions as those in the first to fourth embodiments are denoted by the same reference numerals, and detailed description thereof is omitted. The equivalent circuit of this embodiment is the same as that of the fourth embodiment.

  FIG. 11 shows four photoelectric conversion units. Each of the first to fourth photoelectric conversion units includes N-type semiconductor regions 1101 to 1104. Transfer gate electrodes 1105 to 1108 are arranged corresponding to the four N-type semiconductor regions 1101 to 1104, respectively. Then, electrons in the N-type semiconductor region 1101 included in the first photoelectric conversion unit and the N-type semiconductor region 1102 included in the second photoelectric conversion unit are transferred to the first FD 1109. The electrons in the N-type semiconductor region 1103 included in the third photoelectric conversion unit and the N-type semiconductor region 1104 included in the second photoelectric conversion unit are transferred to the second FD 1109. The first FD 1109, the second FD 1110, and the gate electrode 111 of the amplification transistor are electrically connected to each other by a connection wiring 1113. Note that the gate electrode 111 of the amplification transistor and the connection wiring 1113 are integrated. The first FD 1109 and the connection wiring 1113 are electrically connected by a shared contact 1114. The second FD 1110 and the connection wiring 1113 are electrically connected by a shared contact 1115. A shared contact is a contact that connects semiconductor regions, a semiconductor region and a gate electrode, or a gate electrode without interposing a wiring layer. In FIG. 11, the second FD 1110 is a common area with the source or drain of the reset transistor. Accordingly, a reset transistor is disposed in the active region 115a in which the photoelectric conversion unit and the FD are disposed.

  In this embodiment, the first FD 1109 and the second FD 1110 are electrically connected by the connection wiring 1113. According to such a configuration, four photoelectric conversion units share one amplification transistor 207. Therefore, in addition to the effects of the first to third embodiments, the area of the photoelectric conversion unit can be further increased.

  In the above description of Examples 1 to 5, the transfer of charges from the N-type semiconductor region including the N-type semiconductor region to the FD has been described as an example. However, the configuration to which the present invention can be applied is not limited to such a configuration. For example, the present invention can be applied to a transfer unit that transfers charges from an N-type semiconductor region included in a storage region for storing charges to an FD. It can also be applied to a charge transfer unit of a CCD. In addition, the structure of Examples 1-5 can be implemented combining suitably.

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Insulator 101, 102 N type semiconductor region 103, 104 Transfer gate electrode 105 Floating diffusion 106 P type semiconductor region 115 Active region 302 Interface between semiconductor substrate and insulator

Claims (10)

A semiconductor substrate including an active region;
A first semiconductor region of a first conductivity type;
A second semiconductor region of a second conductivity type having a conductivity type different from the first conductivity type;
A third semiconductor region of the first conductivity type;
An insulator disposed on and in contact with the semiconductor substrate;
A transfer gate electrode disposed on the semiconductor substrate via the insulator and controlling transfer of charge from the first semiconductor region to the first floating diffusion;
A transfer gate electrode different from the transfer gate electrode, disposed on the semiconductor substrate via the insulator and controlling transfer of electric charge from the third semiconductor region to a second floating diffusion;
A second-conductivity-type semiconductor region disposed to extend over the first semiconductor region, the second semiconductor region, and the third semiconductor region;
In a solid-state imaging device having
The first semiconductor region, the second semiconductor region, the third semiconductor region, the first floating diffusion , and the second floating diffusion are disposed in the same active region;
A portion of the first semiconductor region is disposed to overlap a portion of the transfer gate electrode;
A part of the third semiconductor region is arranged to overlap a part of the other transfer gate electrode,
The second semiconductor region is disposed adjacent to and between the part of the first semiconductor region and the part of the third semiconductor region,
The distance from the interface between the semiconductor substrate and the insulator to the position of the partial impurity concentration peak of the first semiconductor region is different from the distance from the interface to the position of the impurity concentration peak of the second semiconductor region. ,
The arrangement direction of the first semiconductor region, the second semiconductor region, and the third semiconductor region is such that the charge transfer direction from the first semiconductor region to the first floating diffusion and the third semiconductor region to the first semiconductor region are the first semiconductor region, the second semiconductor region, and the third semiconductor region . 2. A solid-state imaging device characterized by being different from any of the charge transfer directions to the floating diffusion 2 .   2. The distance from the interface to the position of the partial impurity concentration peak of the third semiconductor region is different from the distance from the interface to the position of the impurity concentration peak of the second semiconductor region. The solid-state imaging device described in 1. 3. The solid-state imaging device according to claim 1 , wherein an area of the first semiconductor region is larger than an area of the first floating diffusion. 4.   4. The solid-state imaging device according to claim 1, wherein a part other than the part of the transfer gate electrode overlaps with a part of the second semiconductor region. 5. The solid-state imaging device further includes a fourth semiconductor region of a first conductivity type arranged to overlap the first semiconductor region,
5. The impurity concentration peak position of the fourth semiconductor region and the impurity concentration peak position of the second semiconductor region are different in depth from each other with respect to the interface. The solid-state imaging device according to any one of the above. The solid-state imaging device further includes a second conductivity type fifth semiconductor region disposed so as to overlap the second semiconductor region,
The position of the impurity concentration peak of the fifth semiconductor region, and the position of the first semiconductor region impurity concentration peaks of claims 1 to 5, characterized in that the interface are mutually different depths as a reference The solid-state imaging device according to any one of the above. The solid-state imaging device further includes a sixth semiconductor region of a second conductivity type,
The sixth semiconductor region is disposed so as to overlap the first semiconductor region and the second semiconductor region, and is disposed closer to the interface than the first semiconductor region and the second semiconductor region. The solid-state imaging device according to any one of claims 1 to 6 , wherein the solid-state imaging device is characterized. The solid-state imaging device has a photoelectric conversion unit,
The solid-state imaging device according to any one of claims 1 to 7 , wherein the first semiconductor region constitutes a part of a photoelectric conversion unit. It said second semiconductor region, the solid-state imaging device according to any one of claims 1 to 8, characterized in that it functions as a potential barrier for the charge of the first semiconductor region. It said second semiconductor region, the solid-state imaging according to any one of claims 1 to 9, characterized in that said first an isolation region for electrically isolating the semiconductor region from another element apparatus.

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