. . . "Then a diffusion barrier 110 that is impermeable to moisture and other gases, is deposited to cover the sidewall of the trench 104, part of the cap wafer 100, the shoulder 103, and part of the substrate 10, as shown in cross-sectional view of FIG. 5A and perspective view of FIG. 5B, where the sidewall spacers 170 are not shown." .