The first cell phones from the 1970s weighed several kilos and were by no means handy enough to put in a jacket pocket. The development is well known; the lightest cell phone today weighs less than 100 grams, and the processing power of a smartphone commercially available today could have been used to control the Apollo mission to the moon back then.
The success in miniaturization has led to an explosion in the number of users; the cell phone has gone from being the exclusive status symbol of a few businessmen and politicians to a mass product. This explosion in widening the user base (more resource consumption) has far outstripped the technical success in miniaturization (less resource consumption). Rebound effect. We can see the same effect in many other areas: Cars have become more and more fuel-efficient, but at the same time mileage has increased because driving has become cheaper (and more convenient), and households often own more than one vehicle. Often, therefore, where technical efficiency, process improvements or new production methods have made a product or service cheaper to consume, massification has followed (air travel, electronic devices and the like).