It is seen from Fig.\[Del\_ArbT\]c that there is a phase jump at the tunnel barrier and an additional $\pi $-shift occurs between the phases of S and s layers.

For $d_{F}=3\xi _{F}$ (Fig.\[Del\_ArbT\]d) the position of the weak place shifts from SIs to sFS part of the SIsFS junction. Then the structure starts to operate in the *mode (1b)*. It is seen that the phase drop across SIs part is small, while $\varphi -\chi \approx $ $\pi /2$ across the F layer, as it should be in SFS junctions with SIs and S electrodes.

At the points marked by the letters ’e’ and ’f’, thickness of the s-layer $d_{s}=0.5\xi _{S}$ is less than its critical value. Then superconductivity in the s-spacer is suppressed due to the proximity with the F film and SIsFS device operates in the *mode (2)*. At $d_{F}=\xi _{F}$ (the dot ’e’ in Fig.[Del\_ArbT]{}a and the panel Fig.\[Del\_ArbT\]e) the position of the weak place is located at the SIs part of the structure and there is additional $\pi $-shift of phase across the F film. As a result, the SIsFS structure behaves like an SInFS tunnel $\pi $-junction. Unsuppressed residual value of the pair potential is due 