This is discouraged, read https://support.google.com/admob/answer/6275345?hl=en&ref_topic=2745287.
You can see positioning instructions here: https://github.com/appfeel/admob-google-cordova/wiki/setOptions#options
admob.createBannerView({
publisherId: "ca-app-pub-XXXXXXXXXXXXXXXX/BBBBBBBBBB",
bannerAtTop: true // or false
});
EDIT
You could have an opportunity if you summit your app to custom search ads and get approved: https://developers.google.com/custom-search-ads/docs/android/