  Moir\'e fringes are used throughout a wide variety of applications in physics
and engineering to bring out small variations in an underlying lattice by
comparing with another reference lattice. This method was recently demonstrated
in Scanning Transmission Electron Microscopy imaging to provide local strain
measurement in crystals by comparing the crystal lattice with the scanning
raster that then serves as the reference. The images obtained in this way
contain a beating fringe pattern with a local period that represents the
deviation of the lattice from the reference. In order to obtain the actual
strain value, a region containing a full period of the fringe is required,
which results in a compromise between strain sensitivity and spatial
resolution. In this paper we propose an advanced setup making use of an
optimised scanning pattern and a novel phase stepping demodulation scheme. We
demonstrate the novel method on a series of 16 nm Si-Ge semiconductor FinFET
devices in which strain plays a crucial role in modulating the charge carrier
mobility. The obtained results are compared with both Nano-beam diffraction and
the recently proposed Bessel beam diffraction technique. The setup provides a
much improved spatial resolution over conventional moir\'e imaging in STEM
while at the same time being fast and requiring no specialised diffraction
camera as opposed to the diffraction techniques we compare to.
