According to Wikipedia, "Moore's law is the observation that the number of transistors in a dense integrated circuit doubles approximately every two years." Gordon Moore made that observation in 1970, and as you can see from the figure below, it has been remarkably accurate over the many decades since.
But you cannot just keep making things smaller and smaller to make them faster and faster. At some point, you hit the limit of approaching zero and the fact that it becomes incredibly expensive to produce incredibly small feature sizes. As shown in the figure below, a leading trade magazine, IEEE Spectrum, has reported that transistors could stop shrinking in 2021.
This will mean that faster computers will not be possible based on shrinking geometries. One potential approach, instead of increasing the density of transistors is the approach of making transistors faster by using carbon nanotubes. Electrons move much faster in carbon nanotubes than conventional semiconductor materials. A picture of a research carbon nanotube bridge is shown below.