We Claim:
1. A semiconductor device (1, 2), comprising:
a first base plate (11) comprising a conductor;
a first semiconductor element (21) having a first electrode surface that is electrically joined onto the first base plate (11) via a joining material (61);
a second base plate (12) comprising a conductor, the second base plate (12) being away from the first base plate (11);
a second semiconductor element (22) that is adjacent to the first semiconductor element (21) and has a first electrode surface that is electrically joined onto the second base plate (12) via a joining material (64);
a first lead (31) for electrically joining a second electrode surface of the first semiconductor element (21) and the second base plate (12) via a joining material (62, 63);
a current path member (13) for giving and receiving current flowing through both the first semiconductor element (21) and the second semiconductor element (22) to and from outside, the current path member (13) being away from both the first base plate (11) and the second base plate (12);
a second lead (32) for electrically joining a second electrode surface of the second semiconductor element (22) and the current path member (13) via a joining material (65, 66); and
a sealing material (51) for sealing at least the respective structural members, wherein:
a rigidity of the second base plate (12) is higher than a rigidity of the first
lead (31) and a rigidity of the second lead (32);
a boundary line including a gap portion (52) along which the first
semiconductor element (21) and the second semiconductor element (22) are
opposed to each other and extending in a direction in which both the first
semiconductor element (21) and the second semiconductor element (22) are not
opposed to each other intersects the second base plate (12) without intersecting the
first lead (31) and the second lead (32) and
the first lead (31) extends from a joining portion with the first
semiconductor element (21) in a first direction, and the second lead (32) extends

2. The semiconductor device (1, 2) as claimed in claim 1, wherein the second base plate (12) intersects a portion of the boundary line at a location other than the gap portion (52).
3. The semiconductor device (1, 2) as claimed in claim 1 or 2, wherein a rigidity of a portion of the second base plate (12), which intersects the boundary line, is lower than rigidities of other portions in the second base plate (12).
4. The semiconductor device as claimed in any one of claims 1 to 3, wherein a portion of the second base plate (12), which intersects the boundary line, comprises a bent portion (124) for absorbing stress.
5. The semiconductor device (1, 2) as claimed in any one of claims 1 to 4, wherein:
the first semiconductor element (21) and the second semiconductor element (22) are located so as to be point symmetric with respect to the gap portion (52); and
the first lead (31) and the second lead (32) are aligned with the boundary line such that the first lead (31) is disposed in parallel with the second lead (32).
6. The semiconductor device (1, 2) as claimed in any one of claims 1 to 5, wherein at least any one of a joining portion of the second base plate (12) with the first lead (31) and a joining portion of the current path member (13) with the second lead (32) comprises a protruding portion (121, 131).
7. The semiconductor device (2) as claimed in any one of claims 1 to 6, wherein a rigidity of a portion formed between both the joining portions in the first lead (31) or the second lead (32) is lower than rigidities of other portions in the first lead (31) or the second lead (32).
8. The semiconductor device (2) as claimed in any one of claims 1 to 7, wherein a portion formed between both the joining portions in the first lead (31) or the second lead (32) comprises a bent portion (311, 321) for absorbing stress.

9. The semiconductor device (1, 2) as claimed in any one of claims 1 to 8, wherein the
first semiconductor element (21) and the second semiconductor element (22) are MOS-
FETs.
10. An inverter device (3), comprising the semiconductor device (1) as claimed in any
one of claims 1 to 9.
11. The inverter device as claimed in claim 10, comprising:
a plurality of the semiconductor devices (1) located on one plane and on
concentric circles;
part of one of each of the first base plates (11) and each of the current path members (13) exposed from the sealing material (51), the part extending toward an inside of the concentric circles with respect to the plurality of the semiconductor devices (1); and
one electric power supply member (91) that is provided on the plane so as to be opposed to the part of the one of each of the first base plates (11) and each of the current path members (13) which are exposed, connected to one electrode of a direct current power supply, and also electrically joined to the part of the one of each of the first base plates (11) and each of the current path members (13) which are exposed in two or more of the plurality of the semiconductor devices (1).
12. The inverter device as claimed in claim 11, comprising:
a pair of the semiconductor devices (1) having a plane symmetric structure with a
plane perpendicular to the plane being a plane of symmetry, the pair of the semiconductor devices being located so as to be adjacent to each other; and
another electric power supply member (92) that is provided on the plane and outside the concentric circles with respect to the plurality of the semiconductor devices (1), connected to another electrode of the direct current power supply, and also electrically joined to part of another of the one of each of the first base plates (11) and each of the current path members (13) which are exposed,
wherein joining portions at which the part of the another of the one of each of the first base plates (11) and each of the current path members (13) which are exposed are electrically joined to the another electric power supply member (92) are located off lines

13. A rotating electrical machine for a vehicle (4) comprising the inverter device (3) as claimed in any one of claims 10 to 12.