Abstract:
Disclosed is a semiconductor device including: a semiconductor substrate; first and second element isolating trenches that are formed in one main surface of the semiconductor substrate separately from each other; a first insulating material that is formed within the first element isolating trench; a plurality of first element formation regions that are surrounded by the first element isolating trench; first semiconductor elements that are respectively formed in the first element formation regions; a second insulating material that is formed within the second element isolating trench; a second element formation region that is surrounded by the second element isolating trench; a second semiconductor element that is formed in the second element formation region; and a stress relaxation structure that is formed between the first element isolating trench and the second element isolating trench.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 USC 119 from Japanese Patent Application No. 2012-134998 filed on Jun. 14, 2012, the disclosure of which is incorporated by reference herein. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, relates to a semiconductor device including an element isolating trench structure and a method of manufacturing the same. 
     2. Related Art 
     Various semiconductor devices including element isolating trench structures are proposed (see Japanese Patent Application Laid-Open (JP-A) Nos. 2009-164609, 2003-303830 and 2001-199191). 
     The present inventors have found that there is the following problem as a result of intensively investigating the semiconductor devices including such element isolating trench structures. That is, when such an element isolating trench structure is arranged to be of two-dimensionally high density, it has been found that there is a problem in that a crack is generated in a trench adjacent to the trench structure which is high densely arranged. 
     SUMMARY 
     According to an aspect of the present invention, there is provided a semiconductor device including: 
     a semiconductor substrate; 
     first and second element isolating trenches that are formed in one main surface of the semiconductor substrate separately from each other; 
     a first insulating material that is formed within the first element isolating trench; 
     a plurality of first element formation regions that are surrounded by the first element isolating trench; 
     first semiconductor elements that are respectively formed in the first element formation regions; 
     a second insulating material that is formed within the second element isolating trench; 
     a second element formation region that is surrounded by the second element isolating trench; 
     a second semiconductor element that is formed in the second element formation region; and 
     a stress relaxation structure that is formed between the first element isolating trench and the second element isolating trench. 
     According to another aspect of the present invention, there is provided a semiconductor device including: 
     a semiconductor substrate; 
     first and second element isolating trenches that are formed in one main surface of the semiconductor substrate separately from each other; 
     a first insulating material that is formed within the first element isolating trench; 
     a plurality of first element formation regions that are surrounded by the first element isolating trench; 
     first semiconductor elements that are respectively formed in the first element formation regions; 
     a second insulating material that is formed within the second element isolating trench; 
     a second element formation region that is surrounded by the second element isolating trench; and 
     a second semiconductor element that is formed in the second element formation region, 
     wherein the second element isolating trench includes a trench formed in the one main surface so as to be inclined at an angle of θ (0°&lt;θ&lt;90°) with respect to a direction perpendicular to a direction toward the second element isolating trench from the first element isolating trench. 
     According to still another aspect of the present invention, there is provided a method of manufacturing a semiconductor device including: 
     forming a structure in one main surface of a semiconductor substrate, the structure including first and second element isolating trenches that are separated from each other, a first insulating material that is formed within the first element isolating trench, a plurality of first element formation regions that are surrounded by the first element isolating trench, a second insulating material that is formed within the second element isolating trench, a second element formation region that is surrounded by the second element isolating trench, and a stress relaxation structure that is formed between the first element isolating trench and the second element isolating trench; and 
     thereafter forming first semiconductor elements in the first element formation regions respectively, and forming a second semiconductor element in the second element formation region. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein: 
         FIG. 1  is a schematic plan view for explaining semiconductor devices according to first to fourth embodiments of the present invention; 
         FIG. 2  is a schematic partially enlarged view of  FIG. 1 ; 
         FIG. 3  is a schematic partially enlarged view of part A in  FIG. 2 ; 
         FIG. 4  is a schematic cross-sectional view taken along line BB of  FIG. 2 ; 
         FIG. 5  is a schematic plan view for explaining a problem of a semiconductor device for comparison; 
         FIG. 6  is a schematic partially enlarged plan view for explaining the semiconductor device according to the second embodiment of the present invention; 
         FIG. 7  is a schematic cross-sectional view taken along line CC of  FIG. 6 ; 
         FIG. 8  is a schematic partially enlarged plan view for explaining the semiconductor device according to the third embodiment of the present invention; 
         FIG. 9  is a schematic cross-sectional view taken along line DD of  FIG. 8 ; 
         FIG. 10  is a schematic partially enlarged plan view for explaining the semiconductor device according the fourth embodiment of the present invention; 
         FIG. 11  is a schematic cross-sectional view taken along line EE of  FIG. 10 ; 
         FIG. 12  is a schematic partially enlarged plan view for explaining a semiconductor device according to a fifth embodiment of the present invention; 
         FIG. 13  is a schematic cross-sectional view for explaining a bipolar transistor which is preferably formed in an element formation region in the semiconductor devices according to the first to fourth embodiments of the present invention; and 
         FIG. 14  is a schematic cross-sectional view for explaining a MOS transistor which is preferably formed in the element formation region in the semiconductor devices according to the first to fifth embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. 
     Referring to  FIG. 1 , in a semiconductor device  1  according to first to fourth preferred embodiments of the present invention, element isolating trench structures  20  for an I/O element are respectively provided at four sides of the peripheral portion of a semiconductor chip  10 , and an element isolating trench structure  30  is provided in the central portion thereof. In the element isolating trench structure  20 , a region surrounded by an element isolating trench  22  serves as an element formation region  26  for an I/O element. An element isolating trench  24  located between the element formation regions  26  adjacent to each other is shared by the element formation regions  26  adjacent to each other. The element isolating trench structure  20  is used for an I/O element, and thus the element formation region  26  is larger than the element formation region of the element isolating trench structure  30  located in the central portion. 
     Element formation regions  38  and  39  of the element isolating trench structure  30  located in the central portion are smaller than the element formation region  26  of the element isolating trench structure  20  for an I/O element, and the element formation regions  38  and  39  disposed collectively are densely packed. In the element isolating trench structure  30 , an element isolating trench structure  32  and an element isolating trench structure  34  are alternately disposed. 
     An element isolating trench  36  of the element isolating trench structure  32  includes element isolating trenches  361  and  362  extending in a Y direction, and an element isolating trench  363  extending in an X direction. Meanwhile, the X direction and the Y direction are at a right angle to each other. A region surrounded by the element isolating trenches  361  and  362  and the element isolating trenches  363  and  363  serves as the element formation region  38 . The element isolating trench  363  located between the element formation regions  38  adjacent to each other is shared by the element formation regions  38  adjacent to each other. In the element isolating trench structure  32 , the element formation regions  38  are arranged parallel in a line in the Y direction. 
     The element isolating trench  36  of the element isolating trench structure  34  includes the element isolating trenches  361  and  362  extending in the Y direction, and an element isolating trench  364  extending in the X direction. A region surrounded by the element isolating trenches  361  and  362  and the element isolating trenches  364  and  364  serves as the element formation region  39 . The element isolating trench  364  located between the element formation regions  39  adjacent to each other is shared by the element formation regions  39  adjacent to each other. In the element isolating trench structure  34 , the element formation regions  39  are arranged parallel in a line in the Y direction. The element formation region  38  of the element isolating trench structure  32  and the element formation region  39  of the element isolating trench structure  34  share the element isolating trench  361  or the element isolating trench  362  located between the element formation region  38  and the element formation region  39 . The element isolating trench  363  of the element isolating trench structure  32  and the element isolating trench  364  of the element isolating trench structure  34  are alternately disposed in the Y direction. The element isolating trench  363  and the element isolating trench  361  or the element isolating trench  362  intersect each other in a T-shape, and the element isolating trench  364  and the element isolating trench  361  or the element isolating trench  362  intersect each other in a T-shape. With such a structure having a T-shaped intersection, the embeddability of the element isolating trench in the intersection portion is better than that in a cross-shaped intersection portion. 
     Stress relaxation structures  40  are respectively provided between the element isolating trench structure  30  located in the central portion of the semiconductor chip  10  and the element isolating trench structures  20  for an I/O element disposed at four sides of the peripheral portion. In other words, places to which the element isolating trench structures  20  for an I/O element are opposite in the outer circumference of the element isolating trench structure  30  are provided with the stress relaxation structures  40  along the element isolating trench structure  30  and the element isolating trench structures  20  for an I/O element. 
     First Embodiment 
     Referring to  FIG. 2 , in the present embodiment, a corrugated trench pattern structure  410  is provided as the stress relaxation structure  40  provided between the element isolating trench structure  30  and the element isolating trench structure  20 . The corrugated trench pattern structure  410  includes a trench  412  inclined at an angle θ1 counterclockwise from the X direction, and a trench  414  inclined at an angle θ2 clockwise from the X direction. The relation of 0°&lt;θ1&lt;90° is established, and the relation of 0°&lt;θ2&lt;90° is established. The trench  412  and the trench  414  are disposed so as not to be horizontal nor perpendicular to the element isolating trenches  361 ,  362 ,  363 , and  364  of the element isolating trench structure  30 . Herein, θ1 and θ2 are preferably 45°. When these angles are 45°, stress (stress) may be uniformly dispersed in both the X direction and the Y direction. Each of the dimensions of the trench  412  and the trench  414  is preferably configured such that, for example, a width W in the short-side direction is approximately 1 μm, a width L in the long-side direction is equal to or more than 4 μm, a depth is equal to or more than 10 μm, and a distance S between the element isolating trench structure  30  and the trenches  412  and  414  is equal to or more than 2 μm. 
     Referring to  FIG. 4 , the element isolating trench  36  is formed in one main surface  101  of a silicon substrate  100 . The one main surface  101  of the silicon substrate  100  and the side face and the bottom face of the element isolating trench  36  are covered with a silicon oxide film  110  formed by thermal oxidation or the like. A silicon oxide film  120  embedded by a CVD method or the like is formed within the element isolating trench  36  covered with the silicon oxide film  110 . After the silicon oxide film  120  is formed on the entirety of the surface by a CVD method or the like, the silicon oxide film  120  on the one main surface  101  of the silicon substrate  100  is removed by performing a planarization process. The dimensions of the element isolating trench  36  have, for example, a depth of equal to or more than 10 μm, a width of approximately 1 μm, and a distance between this element isolating trench  36  and the adjacent one of equal to or more than 2 μm. The dimensions are applicable to the element isolating trenches  361 ,  362 ,  363 , and  364 . Meanwhile, such a deep trench is used not only for a purpose of element isolation, but also for a purpose of dense disposition below a pad to reduce the capacity between the pad and the substrate. In addition, the trench  412  and the trench  414  of the stress relaxation structure  40  also include a similar structure. That is, the trenches  412  and  414  are formed on the one main surface  101  of the silicon substrate  100 . The one main surface  101  of the silicon substrate  100  and the side faces and the bottom faces of the trenches  412  and  414  are covered with the silicon oxide film  110  formed by thermal oxidation or the like. The silicon oxide film  120  embedded by a CVD method or the like is formed within the trenches  412  and  414  covered with the silicon oxide film  110 . Further, the element isolating trench structure  20  also includes a similar structure. That is, the element isolating trench  22  is formed in the one main surface  101  of the silicon substrate  100 . The one main surface  101  of the silicon substrate  100  and the side face and the bottom face of the element isolating trench  22  are covered with the silicon oxide film  110  formed by thermal oxidation or the like. The silicon oxide film  120  embedded by a CVD method or the like is formed within the element isolating trench  22  covered with the silicon oxide film  110 . 
     In the element isolating trench structure  30  in which the element formation regions  38  and  39  are densely packed and the element isolating trenches  36  ( 361 ,  362 ,  363 , and  364 ) are densely disposed, the silicon oxide film  120  is contracted by heat treatment such as annealing, and thus the silicon substrate  110  receives stress  210  from the silicon oxide film  120 . The influence of this stress becomes larger as the element isolating trenches  36  ( 361 ,  362 ,  363 , and  364 ) are more densely packed. For this reason, as shown in  FIG. 5 , the stress reaches a peak at the outside of the element isolating trench structure  30 , the stress  210  is concentrated on the element isolating trench  22  of the element isolating trench structure  20  adjacent to the element isolating trench structure  30 , and thus a crack  400  is generated. 
     Referring to  FIG. 3 , in the present embodiment, as mentioned above, the corrugated trench pattern structure  410  is provided as the stress relaxation structure  40  between the element isolating trench structure  30  and the element isolating trench structure  20 . The corrugated trench pattern structure  410  includes the trench  412  inclined at an angle θ1 counterclockwise from the X direction, and the trench  414  inclined at an angle θ2 clockwise from the X direction. Therefore, the stress  210  received from the element isolating trench structure  30  by the element isolating trench structure  20  may be dispersed into a component  211  parallel to the trench  412  and a component  212  perpendicular thereto by the trench  412 , and may be dispersed into a component  214  parallel to the trench  414  and a component  213  perpendicular thereto by the trench  414 . For example, when θ1 and θ2 are 45°, the stresses  211  to  214  are approximately 0.7 times the stress  210 . As a result, it is possible to prevent a crack from being generated in the element isolating trench structure  20  due to the stress caused by the element isolating trench structure  30 . 
     Next, a method of manufacturing the semiconductor device  1  according to the present embodiment will be described. Referring to  FIGS. 1 and 4 , the element isolating trench  22 , the element isolating trench  36  and the trenches  412  and  414  are first formed in one main surface  101  of the silicon substrate  100 . Thereafter, the silicon oxide film  110  is formed by thermal oxidation or the like, on the one main surface  101  of the silicon substrate  100 , the side face and the bottom face of the element isolating trench  22 , the side face and the bottom face of the element isolating trench  36  and the side faces and the bottom faces of the trenches  412  and  414 . Thereafter, the silicon oxide film  120  is formed on the entirety of the surface by a CVD method or the like. Thereafter, the silicon oxide film  120  on the one main surface  101  of the silicon substrate  100  is removed by performing a planarization process to form a structure in which the silicon oxide film  120  is embedded in the element isolating trench  22  covered with the silicon oxide film  110 , the silicon oxide film  120  is embedded in the element isolating trench  36  covered with the silicon oxide film  110 , and the silicon oxide film  120  is embedded in the trenches  412  and  414  covered with the silicon oxide film  110 . Thereafter, a bipolar transistor, a MOS transistor or the like is formed in the element formation regions  38  and  39 . 
     Second Embodiment 
     Referring to  FIG. 6 , in the present embodiment, a silicon nitride film  420  is provided as the stress relaxation structure  40  provided between the element isolating trench structure  30  and the element isolating trench structure  20 . As shown in  FIG. 7 , the silicon nitride film  420  is an example of a compressive stress application structure in which stress  220  in a compression direction is applied to the silicon substrate  100 . The silicon nitride film  420  is formed on the silicon oxide film  110  formed on the one main surface  101  of the silicon substrate  100  by thermal oxidation or the like. The silicon nitride film  420  is formed, using, for example, a CVD method, between the embedment of the element isolating trench  36  and heat treatment such as annealing. Preferably, the thickness of the silicon nitride film  420  is equal to or more than 1000 Å, the width is equal to or more than 1 μm, and the distance between the element isolating trench structure  30  and the element isolating trench structure  20  is equal to or less than 1 μm. 
     The silicon nitride film  420  that applies the stress  220  in a compression direction to the silicon substrate  100  is provided between the element isolating trench structure  30  and the element isolating trench structure  20 , and thus the stress  220  in a compression direction is applied to the silicon substrate  100  by the silicon nitride film  420 . Since this stress  220  acts as stress in a direction opposite to that of the stress  210  received from the element isolating trench structure  30  by the element isolating trench structure  20 , the stress  210  received from the element isolating trench structure  30  by the element isolating trench structure  20  is relaxed by the stress  220 , and thus a crack may be prevented from being generated. 
     Next, a method of manufacturing the semiconductor device  1  according to the present embodiment will be described. Referring to  FIGS. 1 ,  6 , and  7 , the element isolating trench  22  and the element isolating trench  36  are first formed in one main surface  101  of the silicon substrate  100 . Thereafter, the silicon oxide film  110  is formed by thermal oxidation or the like, on the one main surface  101  of the silicon substrate  100 , the side face and the bottom face of the element isolating trench  22  and the side face and the bottom face of the element isolating trench  36 . Thereafter, the silicon oxide film  120  is formed on the entirety of the surface by a CVD method or the like. Thereafter, the silicon oxide film  120  on the one main surface  101  of the silicon substrate  100  is removed by performing a planarization process to form a structure in which the silicon oxide film  120  is embedded in the element isolating trench  22  covered with the silicon oxide film  110 , and the silicon oxide film  120  is embedded in the element isolating trench  36  covered with the silicon oxide film  110 . Thereafter, a silicon nitride film is formed using, for example, a CVD method, and then is processed into a predetermined pattern to form the silicon nitride film  420 . Thereafter, a bipolar transistor, MOS transistor or the like is formed in the element formation regions  38  and  39 . 
     Third Embodiment 
     Referring to  FIG. 8 , in the present embodiment, a wide dummy trench structure  430  is provided as the stress relaxation structure  40  provided between the element isolating trench structure  30  and the element isolating trench structure  20 . Referring to  FIG. 9 , a trench  42  is formed in one main surface  101  of the silicon substrate  100  located between the element isolating trench structure  30  and the element isolating trench structure  20 . The one main surface  101  of the silicon substrate  100  and the side face and the bottom face of the trench  42  are covered with the silicon oxide film  110  formed by thermal oxidation or the like. The silicon oxide film  120  embedded by a CVD method or the like is formed within the trench  42  covered with the silicon oxide film  110 . When the silicon oxide film  120  is formed under the conditions in which the silicon oxide film  120  is embedded in the element isolating trenches  36  ( 361 ,  362 ,  363 , and  364 ) (see  FIG. 4 ) covered with the silicon oxide film  110 , the width of the trench  42  in the present embodiment is set to such a width that a gap  124  opened with a width of approximately 0.1 μm is formed in the silicon oxide film  120  within the trench  42 . 
     Since the silicon oxide film  120  within the trench  42  includes the gap  124 , the silicon oxide film  120  does not receive the stress  210  from the element isolating trench structure  30  resulting from the contraction of the silicon oxide film  120  within the element isolating trench structure  30  densely packed with the element isolating trenches  36  during heat treatment such as annealing, and does not also generate stress due to the contraction of the silicon oxide film  120  within the trench  42  in the direction of an arrow  230 . Therefore, the element isolating trench structure  20  does not receive stress, and thus a crack may be prevented from being generated in the element isolating trench structure  20 . In addition, the trench  42  may be formed simultaneously with the element isolating trench  36  of the element isolating trench structure  30  and the element isolating trench  22  of the element isolating trench structure  20 , the silicon oxide film  110  within the trench  42  may be formed simultaneously with the silicon oxide film  110  within the element isolating trench  36  and the silicon oxide film  110  within the element isolating trench  22 , and the silicon oxide film  120  within the trench  42  may be formed simultaneously with the silicon oxide film  120  within the element isolating trench  36  and the silicon oxide film  120  within the element isolating trench  22 . Therefore, there is an advantage of being capable of forming the wide dummy trench structure  430  without adding a process. Meanwhile, the gap  124  is embedded with polycrystalline silicon, or an opening of the gap  124  is blocked up, for example, at the time of the formation of gate polycrystalline silicon, before a wiring process, in other words, after stress relaxation, and thus there is no influence at the time of the formation of wiring due to a step difference based on the gap  124 . That is, the element isolating trench  36  is embedded with different materials such as polycrystalline silicon and the silicon oxide film. 
     Next, a method of manufacturing the semiconductor device  1  according to the present embodiment will be described. Referring to  FIGS. 1 ,  8 , and  9 , the element isolating trench  22 , the element isolating trench  36  and the trench  42  are first formed in the one main surface  101  of the silicon substrate  100 . Thereafter, the silicon oxide film  110  is formed by thermal oxidation or the like, on the one main surface  101  of the silicon substrate  100 , the side face and the bottom face of the element isolating trench  22 , the side face and the bottom face of the element isolating trench  36  and the side face and the bottom face of the trench  42 . Thereafter, the silicon oxide film  120  is formed on the entirety of the surface by a CVD method or the like. Thereafter, the silicon oxide film  120  on the one main surface  101  of the silicon substrate  100  is removed by performing a planarization process to form a structure in which the silicon oxide film  120  is embedded in the element isolating trench  22  covered with the silicon oxide film  110 , the silicon oxide film  120  is embedded in the element isolating trench  36  covered with the silicon oxide film  110 , and the silicon oxide film  120  is embedded in the trench  42  covered with the silicon oxide film  110 . At this time, the trench  42  has a larger width than those of the element isolating trench  36  and the element isolating trench  22 , and the gap  124  is formed in the silicon oxide film  120  within the trench  42 . Thereafter, a bipolar transistor, a MOS transistor or the like is formed in the element formation regions  38  and  39 . Taking an example of a case where a MOS transistor is formed, at the time of the formation of gate polycrystalline silicon, the gap  124  is embedded with polycrystalline silicon, or an opening of the gap  124  is blocked up by polycrystalline silicon. 
     Fourth Embodiment 
     Referring to  FIG. 10 , in the present embodiment, a dummy trench structure  440  is provided as the stress relaxation structure  40  provided between the element isolating trench structure  30  and the element isolating trench structure  20 . Referring to  FIG. 11 , a trench  44  is formed in one main surface  101  of the silicon substrate  100  located between the element isolating trench structure  30  and the element isolating trench structure  20 . The silicon oxide film  110  is formed on the one main surface  101  of the silicon substrate  100 , and within the element isolating trench  36  of the element isolating trench structure  30  and the element isolating trench  22  of the element isolating trench structure  20 , and the silicon oxide film  120  is embedded in the element isolating trench  36  and the element isolating trench  22 . However, the silicon oxide film  110  and the silicon oxide film  120  are not formed within the trench  44 . The inside of the trench  44  becomes void. The trench  44  is formed by photolithography and anisotropic etching after the silicon oxide film  110  is formed within the element isolating trench  36  and the element isolating trench  22  and the element isolating trench  36  and the element isolating trench  22  are embedded with the silicon oxide film  120  and before heat treatment such as annealing. The depth of the trench  44  is about half the depths of the element isolating trench  36  and the element isolating trench  22 , and the width of the trench  44  is set to such a width that the trench  44  is sufficiently embedded or an opening of the trench  44  is sufficiently blocked up by a process after the heat treatment such as annealing (for example, process of embedding polycrystalline silicon at the time of the formation of gate polycrystalline silicon). For this reason, there is no influence at the time of the formation of wiring due to a step difference. 
     The side face  441  of the trench  44  on the element isolating trench structure  30  side receives stress  240  from the element isolating trench structure  30  resulting from the contraction of the silicon oxide film  120  within the element isolating trench  36  during heat treatment such as annealing, but the side face  442  of the trench  44  on the element isolating trench structure  20  side does not receive stress from the element isolating trench structure  30 . Therefore, the stress from the element isolating trench structure  30  is not applied to the element isolating trench structure  20 . 
     Next, a method of manufacturing the semiconductor device  1  according to the present embodiment will be described. Referring to  FIGS. 1 ,  10 , and  11 , the element isolating trench  22  and the element isolating trench  36  are first formed in the one main surface  101  of the silicon substrate  100 . Thereafter, the silicon oxide film  110  is formed by thermal oxidation or the like, on the one main surface  101  of the silicon substrate  100 , the side face and the bottom face of the element isolating trench  22  and the side face and the bottom face of the element isolating trench  36 . Thereafter, the silicon oxide film  120  is formed on the entirety of the surface by a CVD method or the like. Thereafter the silicon oxide film  120  on the one main surface  101  of the silicon substrate  100  is removed by performing a planarization process to form a structure in which the silicon oxide film  120  is embedded in the element isolating trench  22  covered with the silicon oxide film  110 , and the silicon oxide film  120  is embedded in the element isolating trench  36  covered with the silicon oxide film  110 . Thereafter, the trench  44  is formed by photolithography and anisotropic etching. Thereafter, a bipolar transistor, a MOS transistor or the like is formed in the element formation regions  38  and  39 . Taking an example of a case where a MOS transistor is formed, at the time of the formation of gate polycrystalline silicon, the trench  44  is embedded with polycrystalline silicon, or an opening of the trench  44  is blocked up by polycrystalline silicon. 
     Fifth Embodiment 
     Referring to  FIG. 12 , a semiconductor device  2  according to a fifth preferable embodiment of the present invention includes an element isolating trench structure  30  and an element isolating trench structure  50  for an I/O element. The element isolating trench structure  30  is the same as that in the first embodiment, and thus the description thereof will be omitted. In the element isolating trench structure  50 , a region surrounded by an element isolating trench  52  serves as an element formation region  58  for an I/O element. The element isolating trench structure  50  is used for an I/O element, and thus the element formation region  58  is larger than the element formation regions  38  and  39  of the element isolating trench structure  30  located in the central portion. The element isolating trench  52  includes a trench  54  and a trench  56  which are at right angles to each other. The trench  54  is inclined at an angle θ3 counterclockwise from the X direction, and the trench  54  is inclined at an angle θ4 clockwise from the X direction. The relation of 0°&lt;θ3&lt;90° is established, and the relation of 0°&lt;θ4&lt;90° is established. Herein, θ3 and θ4 are preferably 45°. When these angles are 45°, stress may be uniformly dispersed in both the X direction and the Y direction. 
     In this manner, the element isolating trench  52  includes the trench  54  inclined at the angle θ3 counterclockwise from the X direction and the trench  56  inclined at the angle θ4 clockwise from the X direction. Therefore, stress received from the element isolating trench structure  30  by the element isolating trench structure  50  may be dispersed into a component parallel to the trench  54  and a component perpendicular thereto by the trench  54 , and may be dispersed into a component parallel to the trench  56  and a component perpendicular thereto by the trench  56 . For example, when θ3 and θ4 are 45°, the stress in the Y direction which is received from the element isolating trench structure  30  by the element isolating trench structure  50  may be decreased as much as approximately 0.7 times. As a result, a crack may be prevented from being generated in the element isolating trench structure  50  due to the stress caused by the element isolating trench structure  30 . 
     Meanwhile, the element isolating trench  52  is formed in one main surface of the silicon substrate. The side face and the bottom face of the element isolating trench  52  are covered with a silicon oxide film formed by thermal oxidation or the like, and a silicon oxide film embedded by a CVD method or the like is formed within the element isolating trench  52  covered with the silicon oxide film  110  formed by the thermal oxidation or the like. 
     Next, a method of manufacturing the semiconductor device  2  according to the present embodiment will be described. Referring to  FIG. 12 , the element isolating trench  36  and the element isolating trench  52  are first formed in the one main surface of the silicon substrate. Thereafter, a silicon oxide film is formed by thermal oxidation or the like, on the one main surface of the silicon substrate, the side face and the bottom face of the element isolating trench  36  and the side face and the bottom face of the element isolating trench  22 . Thereafter, a silicon oxide film is formed on the entirety of the surface by a CVD method or the like. Thereafter, the silicon oxide film formed on the one main surface of the silicon substrate by a CVD method or the like is removed by performing a planarization process to form a structure in which the silicon oxide film formed by the CVD method or the like is embedded in the element isolating trench  36  covered with the silicon oxide film formed by thermal oxidation or the like, and the silicon oxide film formed by the CVD method or the like is embedded in the element isolating trench  52  covered with the silicon oxide film formed by thermal oxidation or the like. Thereafter, a bipolar transistor, a MOS transistor or the like is formed in the element formation regions  38  and  39 , and a semiconductor element for I/O is formed in the element formation region  58 . 
     In the above-mentioned first to fifth embodiments, a bipolar transistor or a MOS transistor is formed in the element formation regions  38  and  39 . Though a description is made by taking an example of the element formation region  38 , the same is true of the element formation region  39 . 
     Referring to  FIG. 13 , P −  layer  131  is formed on an N −  substrate  130 . An element isolating trench  363  is formed from the surface of the P −  layer  131  up to the middle of the N −  substrate  130 . A channel stopper  158  is formed in the N −  substrate  130  below the element isolating trench  363 . A region surrounded by the element isolating trenches  363  and  363  and the element isolating trenches  361  and  362  (see  FIGS. 2 and 8 ) serves as the element formation region  38 . An N −  layer  132  is formed in the surface of the P −  layer  131 . A P −  layer  133  is formed in the P −  layer  131  separately from the N −  layer  132 . A Locos oxide film  137  is formed on the surface of the P −  layer  131 . Openings  141 ,  142 , and  144  are formed in the Locos oxide film  137 . A P +  layer  134  is formed on the N −  layer  132  exposed to the opening  141 . An N +  layer  135  is formed on the N −  layer  132  exposed to the opening  142 . A P +  layer  136  is formed on the P −  layer  133  exposed to the opening  144 . The P +  layer  134  functions as an emitter. The N −  layer  132  and the N +  layer  135  function as a base. The P −  layer  133  and the P +  layer  136  function as a collector. An interlayer dielectric film  150  is formed on the Locos oxide film  137 , the P +  layer  134 , the N +  layer  135  and the P +  layer  136 . Contacts  151 ,  152 , and  153  which are respectively connected to the P +  layer  134 , the N +  layer  135  and the P +  layer  136  are formed in through holes provided in the interlayer dielectric film  150 . Metal wirings  154 ,  155 , and  156  which are respectively connected to the contacts  151 ,  152 , and  153  are formed on the interlayer dielectric film  150 . 
     Referring to  FIG. 14 , an N −  layer  161  is formed on a P −  substrate  160 . An element isolating trench  363  is formed from the surface of the N −  layer  161  up to the middle of the P″ substrate  160 . A channel stopper  159  is formed in the N −  substrate  130  below the element isolating trench  363 . A region surrounded by the element isolating trenches  363  and  363  and the element isolating trenches  361  and  362  (see  FIGS. 2 and 8 ) serves as the element formation region  38 . P −  layers  162  and  163  are formed in the surface of the N −  layer  161  separately from each other. A P layer  163  is formed in the layer  162 . A P −  layer  165  is formed in a P −  layer  164 . A Locos oxide film  168  is formed on the surface of the N −  layer  161 . Openings  171 ,  172 , and  173  are formed in the Locos oxide film  168 . A gate oxide film  167  is formed on the N −  layer  161  exposed to the opening  171 . A P +  layer  174  is formed on the P layer  163  exposed to the opening  172 . A P +  layer  175  is formed on the P layer  165  exposed to the opening  173 . The P −  layer  162 , the P layer  163  and the P +  layer  174  function as a source. The P −  layer  164 , the P layer  165  and the P +  layer  175  function as a drain. A polycrystalline silicon layer  176  for a gate electrode is formed on the gate oxide film  167 , a WSi  177  is formed on the polycrystalline silicon layer  176 , and a sidewall  178  is formed on the side faces of the polycrystalline silicon layer  176  and the WSi  177 . 
     As stated above, a variety of typical embodiments of the present invention have been described, but the present invention is not limited to these embodiments. Therefore, the scope of the present invention is intended to be limited only by the following claims.