For enhancing the high performance of a non-volatile semiconductor memory device having an MONOS type transistor, a non-volatile semiconductor memory device is provided with MONOS type transistors having improved performance in which the memory cell of an MONOS non-volatile memory comprises a control transistor and a memory transistor. The image may be presented under an array of spherical or lenticular microlenses so that different images are presented at different viewing angles. A plurality of compression springs are each detachably extended between the fastening means on the drop-in frame. 012 or less where a represents the thickness of the crystal blank in the oscillation region and b represents the thickness of the excitation electrode. In some embodiments of the invention, the polybenzoxazole membranes may be subjected to an additional crosslinking step to increase the selectivity of the membranes.