There are many phenomenologicalmodels of inflation in the literature,which usually employ some new fields and new interactions. It is, therefore, quite reasonable and meaningful to search for the minimal inflationary model building, by getting most economical and viable inflationary scenario. I amgoing to use the one proposed the long time ago by Starobinsky (20; 21), which does not use new fields (beyond a spacetime metric) and exploits only gravitational interactions. I also assume that the general coordinate invariance in spacetime is fundamental, and it should not be sacrificed. Moreover, it should be extended to the more fundamental, local supersymmetry that is known to imply the general coordinate.
