Conventionally, semiconductor devices of this type with an acceleration sensing part have been proposed (see, for example, Patent Literature 1). More specifically, in this semiconductor device, a sensing part that detects acceleration is disposed between the first substrate and the second substrate. A first pad portion electrically connected to the sensing part is formed on the first substrate, and a second pad portion is formed on the second substrate in a portion opposite to the first pad portion. The first pad portion and the second pad portion are bonded together and electrically connected. The first pad portion and the second pad portion are formed of a material mainly composed of aluminum.
Since the first pad portion and the second pad portion are formed of a material mainly composed of aluminum in such a semiconductor device, the oxide film (natural oxide film) formed on the surface of the first pad portion and the second pad portion is very hard. When bonding the first pad portion and the second pad portion together, the oxide film formed on the first and second pad portions need to be removed before joining them so as to electrically connect the first and second pad portions. To remove the oxide film, the temperature has to be raised very high before or during the bonding of the first and second pad portions, or a very large load must be applied during the bonding. Subjecting the sensing part to such a state may possibly change its characteristics.