The definition of `Moore's Law' has come to refer to almost anything related to the semiconductor industry that when plotted on semi-log paper approximates a straight line. I hesitate to review its origins and by doing so restrict its definition. However, this paper is a review of the history and past performance relative to predictions and shows where the advances have come from. I will leave the future performance up to you. Certainly continuing on the same slope doesn't get any easier. It presents a difficult challenge to the industry.
Gordon E. Moore,
"Lithography and the future of Moore's law", Proc. SPIE 2438, Advances in Resist Technology and Processing XII, (9 June 1995); doi: 10.1117/12.210341; https://doi.org/10.1117/12.210341