Google is now launching lead generation ads for Search. Previously you could only use lead generation for ad extensions.
Now you will be able to show a lead form when a user taps the headline of your search ad. To start using these you need to create a Search campaign with Leads as your goal. You’ll then need to create a lead form extension. Once your lead form is created you can go to your settings and choose “always show the lead form when someone interacts with my ad.” Once someone submits your form they will be given the option to visit your site or return to search results.