Gulp clean css creates duplicate style.min.css files

When I run gulp default task, gulp clean css creates first style.min.css. When I end this task and start again it creates styles.min.min.css and it happend continuously with adding .min every time so it create multiple style files. Here is my gulpfile.js:

    gulp.task('sass', function () {

                // Global Theme CSS Compilation

   gulp.task('minify', function () {            
                // CSS Minify          
     .pipe(minifyCss()).pipe(rename({suffix: '.min'})).pipe(gulp.dest('./css'));

        gulp.task('watch',['sass'], function(){
  ['./sass/global/**/*.scss', './sass/themes/construction/*.scss', './sass/themes/corporate/*.scss']);

What I need to do to prevent gulp create multiple files but just one and just update it?

You simply forgot a back slash in this line:

gulp.src(['./css/*.css',  '!./css/*.min.css'])

in the negation part of the glob.