1. Field of the Invention
The present invention relates to a process for manufacturing a semiconductor device and, more specifically, it relates to a process for manufacturing a semiconductor device wherein semiconductor elements are laminated together in a stage of semiconductor wafers and capable to be mounted.
2. Description of the Related Art
As shown in FIGS. 6(a) to 6(c), there is a product wherein semiconductor elements 12 (FIG. 6b) are carried on a flexible wiring board 10 (FIG. 6a) provided with external connection terminals 14 in a mounting area and the flexible wiring board 10 is folded as shown in FIG. 6c to stack the semiconductor elements 12 together (for example, in Japanese Unexamined Patent Publication (Kokai) Nos. 2000-307037, 2003-86760 and 2003-86761). Since a plurality of semiconductor elements can be mounted on one semiconductor device, the semiconductor device formed by stacking the semiconductor elements in such a manner is advantageous in that it is compact in size and large in capacity.
A recent semiconductor element is made extremely thin, such as 100 μm or less, by grinding, and it is possible to form a sufficiently small semiconductor device by stacking together a plurality of the semiconductor elements.
As mentioned above, a method for mounting a plurality of stacked semiconductor elements on a single semiconductor device is effective for forming a highly integrated semiconductor device small in size. However, the prior art method for forming the semiconductor device by carrying a plurality of semiconductor elements on a flexible wiring board and folding the latter is problematic because this method needs a flexible wiring board having a predetermined wiring pattern and accurate positioning of the semiconductor elements to the flexible wiring board, and the production and assembly, of the respective parts, are costly.